DS1923

DS1923 MAXIM | Alldatasheet

Document overview

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Technical content

Features

♦ Digital Hygrometer Measures Humidity with 8-Bit (0.6%RH) or 12-Bit (0.04%RH) Resolution ♦ Operating Range: -20°C to +85°C; 0 to 100%RH (see Safe Operating Range Graph) ♦ Automatically Wakes Up, Measures Temperature and/or Humidity, and Stores Values in 8KB of Data-Log Memory in 8-Bit or 16-Bit Format ♦ Digital Thermometer Measures Temperature with 8-Bit (0.5°C) or 11-Bit (0.0625°C) Resolution ♦ Temperature Accuracy Better Than ±0.5°C from -10°C to +65°C with Software Correction ♦ Built-In Capacitive Polymer Humidity Sensor for Humidity Logging ♦ Hydrophobic Filter Protects Sensor Against Dust, Dirt, Contaminants, and Water Droplets/Condensation ♦ Sampling Rate from 1s Up to 273hr ♦ Programmable Recording Start Delay After Elapsed Time or Upon a Temperature Alarm Trip Point ♦ Programmable High and Low Trip Points for Temperature and Humidity Alarms ♦ Quick Access to Alarmed Devices Through 1-Wire Conditional Search Function ♦ 512 Bytes of General-Purpose Memory Plus 64 Bytes of Calibration Memory ♦ Two-Level Password Protection of All Memory and Configuration Registers ♦ Communicates to Host with a Single Digital Signal at Up to 15.4kbps at Standard Speed or Up to 125kbps in Overdrive Mode Using 1-Wire Protocol ♦ Individually Calibrated in an NIST-Traceable Chamber ♦ Calibration Coefficients for Temperature and Humidity Factory Programmed Into Nonvolatile (NV) Memory Common iButton Features ♦ Digital Identification and Information by Momentary Contact ♦ Unique Factory-Lasered 64-Bit Registration Number Ensures Error-Free Device Selection and Absolute Traceability Because No Two Parts Are Alike ♦ Built-In Multidrop Controller for 1-Wire Net ♦ Chip-Based Data Carrier Compactly Stores Information ♦ Data Can Be Accessed While Affixed to Object ♦ Button Shape is Self-Aligning with Cup-Shaped Probes ♦ Durable Stainless-Steel Case Engraved with Registration Number Withstands Harsh Environments ♦ Easily Affixed with Self-Stick Adhesive Backing, Latched by Its Flange, or Locked with a Ring Pressed Onto Its Rim ♦ Presence Detector Acknowledges When Reader First Applies Voltage ♦ Meets UL 913 (4th Edit.); Intrinsically Safe Apparatus: Approved Under Entity Concept for Use in Class I, Division 1, Group A, B, C, and D Locations

Ordering Information

Pin Configuration appears at end of data sheet. #Denotes a RoHS-compliant device that may include lead(Pb) that is exempt under the RoHS requirements. Examples of Accessories iButton and 1-Wire are registered trademarks of Maxim Integrated Products, Inc. PART ACCESSORY DS9096P Self-Stick Adhesive Pad DS9101 Multipurpose Clip DS9093RA Mounting Lock Ring DS9093A Snap-In FOB DS9092 i Button Probe PART TEMP RANGE PIN-PACKAGE DS1923-F5# -20°C to +85°C F5 i Button

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VPUP = +3.0V to +5.25V, TA = -20°C to +85°C.) Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Operating Temperature Storage Temperature PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS IO PIN: GENERAL DATA 1-Wire Pullup Resistance R PUP (Notes 1, 2) 2.2 k Input Capacitance C IO (Note 3) 100 800 pF Input Load Current I L IO pin at VPUP 6 10 μA High-to-Low Switching Threshold V TL (Notes 4, 5) 0.4 3.2 V Input Low Voltage V IL (Notes 1, 6) 0.3 V Low-to-High Switching Threshold V TH (Notes 4, 7) 0.7 3.4 V Switching Hysteresis V HY (Note 8) 0.09 N/A V Output Low Voltage V OL At 4mA (Note 9) 0.4 V Standard speed, RPUP = 2.2k 5 Overdrive speed, R PUP = 2.2k 2 Recovery Time (Note 1) tREC Overdrive speed directly prior to reset pulse, R PUP = 2.2k 5 μs Rising-Edge Hold-Off Time t REH (Note 10) 0.6 2.0 μs Standard speed 65 Overdrive speed, VPUP > 4.5V 8 Time-Slot Duration (Note 1) t SLOT Overdrive speed (Note 11) 9.5 μs IO PIN: 1-Wire RESET, PRESENCE-DETECT CYCLE Standard speed, VPUP > 4.5V 480 720 Standard speed (Note 11) 690 720 Overdrive speed, VPUP > 4.5V 48 80 Reset Low Time (Note 1) t RSTL Overdrive speed (Note 11) 70 80 μs Standard speed, VPUP > 4.5V 15 60 Standard speed (Note 11) 15 63.5 Presence-Detect High Time t PDH Overdrive speed (Note 11) 2 7 μs Standard speed, VPUP > 4.5V 1.5 5 Standard speed 1.5 8Presence-Detect Fall Time (Note 12) tFPD Overdrive speed 0.15 1 μs *See the Safe Operating Range graph.

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory ELECTRICAL CHARACTERISTICS (continued) (VPUP = +3.0V to +5.25V, TA = -20°C to +85°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Standard speed, VPUP > 4.5V 60 240 Standard speed (Note 11) 60 287 Overdrive speed, VPUP > 4.5V (Note 11) 7 24 Presence-Detect Low Time t PDL Overdrive speed (Note 11) 72 8 μs Standard speed, VPUP > 4.5V 65 75 Standard speed 71.5 75Presence-Detect Sample Time (Note 1) tMSP Overdrive speed 8 9 μs IO PIN: 1-Wire WRITE Standard speed 60 120 Overdrive speed, VPUP > 4.5V (Note 11) 6 12Write-Zero Low Time (Note 1) tW0L Overdrive speed (Note 11) 7.5 12 μs Standard speed 5 15 - Write-One Low Time (Notes 1, 13) tW1L Overdrive speed 1 1.95 - μs IO PIN: 1-Wire READ Standard speed 5 15 - Read Low Time (Notes 1, 14) tRL Overdrive speed 1 1.95 - μs Standard speed t RL + 15 Read Sample Time (Notes 1, 14) tMSR Overdrive speed t RL + 1.95 μs REAL-TIME CLOCK (RTC) Accuracy +25°C -3 +3 Min/ Month Frequency Deviation F -20°C to +85°C -300 +60 ppm TEMPERATURE CONVERTER 8-bit mode (Note 15) 30 75 Conversion Time t CONV 16-bit mode (11 bits) 240 600 ms Thermal Response Time Constant RESP i Button package (Note 16) 130 s Conversion Error Without Software Correction (Notes 15, 17, 18, 19) See the Temperature Accuracy graph °C Conversion Error with Software Correction (Notes 15, 17, 18, 19) See the Temperature Accuracy graph °C HUMIDITY CONVERTER (Note 20) Humidity Response Time Constant RH Slow moving air (Note 21) 30 s 8 12 12 Bits RH Resolution (Note 22) 0.64 0.04 0.04 %RH RH Range (Note 23) 0 100 %RH

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory ELECTRICAL CHARACTERISTICS (continued) (VPUP = +3.0V to +5.25V, TA = -20°C to +85°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS RH Accuracy and Interchangeability With software correction (Notes 18, 19, 24, 25, 26) ±5 %RH RH Nonlinearity With software correction (Note 18) < 1 RH Hysteresis (Notes 27, 28) 0.5 %RH RH Repeatability (Note 29) ±0.5 %RH Long-Term Stability At 50%RH (Note 30) < 1.0 %RH/ year Note 1: System requirement. Note 2: Maximum allowable pullup resistance is a function of the number of 1-Wire devices in the system and 1-Wire recovery times. The specified value here applies to systems with only one device and with the minimum 1-Wire recovery times. For more heavily loaded systems, an active pullup such as that in the DS2480B may be required. Note 3: Capacitance on the data pin could be 800pF when VPUP is first applied. If a 2.2kΩ resistor is used to pull up the data line, 2.5μs after VPUP has been applied, the parasite capacitance does not affect normal communications. Note 4: VTL and VTH are a function of the internal supply voltage. Note 5: Voltage below which, during a falling edge on IO, a logic 0 is detected. Note 6: The voltage on IO must be less than or equal to VILMAX whenever the master drives the line low. Note 7: Voltage above which, during a rising edge on IO, a logic 1 is detected. Note 8: After VTH is crossed during a rising edge on IO, the voltage on IO must drop by VHY to be detected as logic 0. Note 9: The I-V characteristic is linear for voltages less than 1V. Note 10: The earliest recognition of a negative edge is possible at tREH after VTH has been previously reached. Note 11: Numbers in bold are not in compliance with the published iButton standards. See the Comparison Table. Note 12: Interval during the negative edge on IO at the beginning of a presence-detect pulse between the time at which the voltage is 90% of VPUP and the time at which the voltage is 10% of VPUP. Note 13: ε in Figure 13 represents the time required for the pullup circuitry to pull the voltage on IO up from VIL to VTH. Note 14: δ in Figure 13 represents the time required for the pullup circuitry to pull the voltage on IO up from VIL to the input high threshold of the bus master. Note 15: To conserve battery power, use 8-bit temperature logging whenever possible. Note 16: This number was derived from a test conducted by Cemagref in Antony, France, in July 2000: Note 17: For software-corrected accuracy, assume correction using calibration coefficients with calibration equations for error compensation. Note 18: Software correction for humidity and temperature is handled automatically using the 1-Wire Viewer Software package available at: http://www.ibutton.com. Note 19: Warning: Not for use as the sole method of measuring or tracking temperature and/or humidity in products and articles that could affect the health or safety of persons, plants, animals, or other living organisms, including but not limited to foods, beverages, pharmaceuticals, medications, blood and blood products, organs, and flammable and combustible products. User shall assure that redundant (or other primary) methods of testing and determining the handling methods, quality, and fitness of the articles and products should be implemented. Temperature and/or humidity tracking with this product, where the health or safety of the aforementioned persons or things could be adversely affected, is only recom- mended when supplemental or redundant information sources are used. Data-logger products are 100% tested and cali- brated at time of manufacture by Maxim to ensure that they meet all data sheet parameters, including temperature accuracy. User shall be responsible for proper use and storage of this product. As with any sensor-based product, user shall also be responsible for occasionally rechecking the accuracy of the product to ensure it is still operating properly. Note 20: All humidity specifications are determined at +25°C except where specifically indicated. Note 21: Response time is determined by measuring the 1/e point as the device transitions from 40%RH to 90%RH or 90%RH to 40%RH, whichever is slower. Test was performed at 5L/min airflow. Note 22: All DS1923 humidity measurements are 12-bit readings. Missioning determines 8-bit or 16-bit data logging. Battery life- time is the same no matter what RH resolution is logged. Note 23: Reliability studies have shown that the device survives a minimum of 1000 cycles of condensation and drying, but this product is not guaranteed for extended use in condensing environments.

Note 24: Software-corrected accuracy is accomplished using the method detailed in the Software Correction Algorithm for Temperature section. Note 25: Every DS1923 device is measured and calibrated in a controlled, NIST-traceable RH environment. Note 26: Higher accuracy versions may be available. Contact the factory for details. Note 27: If this device is exposed to a high humidity environment (> 70%RH), and then exposed to a lower RH environment, the device reads high for a period of time. The device typically reads within +0.5%RH at 20%RH, 30 minutes after being exposed to continuous 80%RH for 30 minutes. Note 28: All capacitive RH sensors can change their reading depending upon how long they have spent at high (> 70%RH) or low RH (< 20%RH). This effect is called saturation drift and can be compensated through software, as described in the Software Saturation Drift Compensation section. Note 29: Individual RH readings always include a noise component (repeatability). To minimize measurement error, average as many samples as is reasonable. Note 30: Like all relative humidity sensors, when exposed to contaminants and/or conditions toward the limits of the safe operating range, accuracy degradation can result (see the Safe Operating Range graph). For maximum long-term stability, the sen- sor should not be exposed or subjected to organic solvents, corrosive agents (e.g., strong acids, SO2, H2SO4, CI2, HCL, H2S) and strong bases (i.e., compounds with a pH greater than 7). Dust settling on the filter surface does not affect the sensor performance except to possibly decrease the speed of response. For more information on the RH sensor’s toler- ance to chemicals visit: http://content.honeywell.com/sensing/prodinfo/humiditymoisture/technical/c15_144.pdf. DS1923 Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory COMPARISON TABLE LEGACY VALUES DS1923 VALUES STANDARD SPEED (μs) OVERDRIVE SPEED (μs) STANDARD SPEED (μs) OVERDRIVE SPEED (μs) PARAMETER MIN MAX MIN MAX MIN MAX MIN MAX tSLOT (including tREC) 61 (undefined) 7 (undefined) 65 (undefined) 9.5 (undefined) tRSTL 480 (undefined) 48 80 690 720 70 80 tPDH 15 60 2 6 15 63.5 2 7 tPDL 60 240 8 24 60 287 7 28 tW0L 60 120 6 16 60 120 7.5 12 *Intentional change; longer recovery time requirement due to modified 1-Wire front-end. Note: Numbers in bold are not in compliance with the published iButton standards. iButton CAN PHYSICAL SPECIFICATION SIZE See the Package Information section. WEIGHT Ca. 5.0 grams SAFETY Meets UL 913 (4th Edit.); Intrinsically Safe Apparatus, approval under Entity Concept for use in Class I, Division 1, Group A, B, C, and D Locations. ELECTRICAL CHARACTERISTICS (continued) (VPUP = +3.0V to +5.25V, TA = -20°C to +85°C.)

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Safe Operating Range 100HUMIDITY (%RH) SAFE OPERATING ZONE STORAGE ONLY -40 -20 0 20 40 60 80 TEMPERATURE (°C) Temperature Accuracy -1.0 - 2 0 - 1 00 1 02 03 04 05 06 07 08 0 -0.5 0.5 1.0 1.5 2.0 NOTE: THE GRAPHS ARE BASED ON 11-BIT DATA. TEMPERATURE (°C) ERROR (°C) UNCORRECTED MAXIMUM ERROR UNCORRECTED MINIMUM ERROR SW CORRECTED MAXIMUM ERROR SW CORRECTED MINIMUM ERROR

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Minimum Lifetime vs. Temperature, Slow Sampling (Temperature Only) 8-BIT MINIMUM PRODUCT LIFETIME (YEARS) 11-BIT MINIMUM PRODUCT LIFETIME (YEARS) EVERY MINUTE EVERY 60 MINUTES EVERY 3 MINUTES NO SAMPLES EVERY 10 MINUTES OSCILLATOR OFF EVERY MINUTE EVERY 60 MINUTES EVERY 3 MINUTES NO SAMPLES EVERY 10 MINUTES OSCILLATOR OFF EVERY 30 MINUTES EVERY 300 MINUTES - 2 0- 1 001 02 03 04 05 06 07 08 0 TEMPERATURE (°C) - 2 0- 1 001 02 03 04 05 06 07 08 0 TEMPERATURE (°C)

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Minimum Lifetime vs. Temperature, Fast Sampling (Temperature Only) 100 150 200 250 300 350 8-BIT MINIMUM PRODUCT LIFETIME (DAYS)11-BIT MINIMUM PRODUCT LIFETIME (DAYS) EVERY SECOND EVERY 30 SECONDS EVERY 3 SECONDS EVERY 60 SECONDS EVERY 10 SECONDS EVERY SECOND EVERY 30 SECONDS EVERY 3 SECONDS EVERY 60 SECONDS EVERY 10 SECONDS - 2 0- 1 001 02 03 04 05 06 07 08 0 TEMPERATURE (°C) - 2 0- 1 001 02 03 04 05 06 07 08 0 TEMPERATURE (°C) 100

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory 8-BIT TEMPERATURE PLUS HUMIDITY MINIMUM PRODUCT LIFETIME (YEARS) EVERY MINUTE EVERY 60 MINUTES NO SAMPLES EVERY 3 MINUTES OSCILLATOR OFF EVERY 10 MINUTES - 2 0- 1 001 02 03 04 05 06 07 08 0 TEMPERATURE (°C) Minimum Lifetime vs. Temperature, Slow Sampling (Temperature with Humidity) 100 150 200 250 300 350 8-BIT TEMPERATURE PLUS HUMIDITY MINIMUM PRODUCT LIFETIME (DAYS) EVERY SECOND EVERY 30 SECONDS EVERY 3 SECONDS EVERY 60 SECONDS EVERY 10 SECONDS - 2 0- 1 001 02 03 04 05 06 07 08 0 TEMPERATURE (°C) Minimum Lifetime vs. Temperature, Fast Sampling (Temperature with Humidity)

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Minimum Product Lifetime vs. Sample Rate (Temperature Only) 0.01 0.01 0.1 1 10 100 0.1 NOTE: WITH HUMIDITY LOGGING ACTIVATED, THE LIFETIME IS REDUCED BY LESS THAN 11% FOR THE SAMPLE RATES OF 3MIN. AND SLOWER, AND BY A MAXIMUM OF 20% FOR SAMPLE RATES OF 1MIN. AND FASTER. 0°C +40°C +60°C +75°C +85°C 0°C +40°C +60°C +75°C +85°C MINUTES BETWEEN SAMPLES 0.01 0.1 1 10 100 NOTE: WITH HUMIDITY LOGGING ACTIVATED, THE LIFETIME IS REDUCED BY A MAXIMUM OF 4%. THE INCREMENTAL ENERGY CONSUMED BY HUMIDITY LOGGING IS INDEPENDENT OF THE HUMIDITY LOGGING RESOLUTION. MINUTES BETWEEN SAMPLES 8-BIT MINIMUM PRODUCT LIFETIME (YEARS)11-BIT MINIMUM PRODUCT LIFETIME (YEARS) 0.001 0.01 0.1

Figure 1. Block Diagram

Figure 6. Register Pages Map

Figure 6. Register Pages Map (continued)

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Detailed Register Descriptions Timekeeping and Calendar The RTC and calendar information is accessed by reading/writing the appropriate bytes in the register page, address 0200h to 0205h. For readings to be valid, all RTC registers must be read sequentially start- ing at address 0200h. Some of the RTC bits are set to 0. These bits always read 0 regardless of how they are written. The number representation of the RTC registers is binary-coded decimal (BCD) format. The DS1923’s RTC can run in either 12hr or 24hr mode. Bit 6 of the Hours register (address 0202h) is defined as the 12hr or 24hr mode select bit. When high, the 12hr mode is selected. In the 12hr mode, bit 5 is the AM/PM bit with logic 1 being PM. In the 24hr mode, bit 5 is the 20hr bit (20hr to 23hr). The CENT bit, bit 7 of the Months register, can be written by the user. This bit changes its state when the years counter transitions from 99 to 00. The calendar logic is designed to automatically com- pensate for leap years. For every year value that is either 00 or a multiple of 4, the device adds a 29th of February. This works correctly up to (but not including) the year 2100. Sample Rate The content of the Sample Rate register (addresses 0206h, 0207h) specifies the time elapse (in seconds if EHSS = 1, or minutes if EHSS = 0) between two tem- perature/humidity-logging events. The sample rate can be any value from 1 to 16,383, coded as an unsigned 14-bit binary number. If EHSS = 1, the shortest time between logging events is 1s and the longest (sample rate = 3FFFh) is 4.55hr. If EHSS = 0, the shortest is 1min and the longest time is 273.05hr (sample rate = 3FFFh). The EHSS bit is located in the RTC Control reg- ister at address 0212h. It is important that the user sets the EHSS bit accordingly while setting the Sample Rate register. Writing a sample rate of 0000h results in a sample rate = 0001h, causing the DS1923 to log the temperature either every minute or every second depending upon the state of the EHSS bit. Sample Rate Register Bitmap ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 0206h Sample Rate Low 0207h 0 0 Sample Rate High RTC Registers Bitmap ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 0200h 0 10 Seconds Single Seconds 0201h 0 10 Minutes Single Minutes 0202h 0 12/24 20 Hour AM/PM 10 Hour Single Hours 0203h 0 0 10 Date Single Date 0204h CENT 0 0 10 Months Single Months 0205h 10 Years Single Years Note: During a mission, there is only read access to these registers. Bit cells marked “0” always read 0 and cannot be written to 1. Note: During a mission, there is only read access to these registers. Bit cells marked “0” always read 0 and cannot be written to 1.

0000h when too cold and FFh or FFE0h when too hot. address 0208h; High Alarm address 0209h). sion is used to determine whether an alarm is generated. Table 1. Temperature Conversion Examples Table 2. Temperature Alarm Threshold Examples

according to the algorithms shown in the table below. Table 3. Humidity Conversion Examples Table 4. Humidity Alarm Threshold Examples Round HALM to the nearest integer. reversed before calculating a humidity alarm threshold. For example, let the desired alarm threshold be 60%RH.

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Temperature Sensor Alarm The DS1923 has two Temperature Alarm Threshold registers (address 0208h, 0209h) to store values that determine whether a critical temperature has been reached. A temperature alarm is generated if the device measures an alarming temperature and the alarm signaling is enabled. The bits ETLA and ETHA that enable the temperature alarm are located in the Temperature Sensor Control register. The temperature alarm flags TLF and THF are found in the Alarm Status register at address 0214h. Bit 1: Enable Temperature High Alarm (ETHA). This bit controls whether, during a mission, the temperature high alarm flag (THF) can be set, if a temperature con- version results in a value equal to or higher than the value in the Temperature High Alarm Threshold register. If ETHA is 1, temperature high alarms are enabled. If ETHA is 0, temperature high alarms are not generated. Bit 0: Enable Temperature Low Alarm (ETLA). This bit controls whether, during a mission, the temperature low alarm flag (TLF) can be set, if a temperature con- version results in a value equal to or lower than the value in the Temperature Low Alarm Threshold register. If ETLA is 1, temperature low alarms are enabled. If ETLA is 0, temperature low alarms are not generated. Humidity Alarm The DS1923 has two Humidity Alarm Threshold regis- ters (address 020Ah, 020Bh) to store values that deter- mine whether humidity readings can generate an alarm. Such an alarm is generated if the humidity data read from the sensor qualifies for an alarm and the alarm signaling is enabled. The bits EHLA and EHHA that enable the humidity alarm are located in the Humidity Sensor Control register. The corresponding alarm flags HLF and HHF are found in the Alarm Status register at address 0214h. Bit 1: Enable Humidity High Alarm (EHHA). This bit controls whether, during a mission, the humidity high alarm flag (HHF) can be set, if a value from the humidi- ty sensor is equal to or higher than the value in the Humidity High Alarm Threshold register. If EHHA is 1, humidity high alarms are enabled. If EHHA is 0, humidi- ty high alarms are not generated. Bit 0: Enable Humidity Low Alarm (EHLA). This bit controls whether, during a mission, the humidity low alarm flag (HLF) can be set, if a value from the humidity sensor is equal to or lower than the value in the Humidity Low Alarm Threshold register. If EHLA is 1, humidity low alarms are enabled. If EHLA is 0, humidity low alarms are not generated. RTC Control To minimize the power consumption of a DS1923, the RTC oscillator should be turned off when the device is not in use. The oscillator on/off bit is located in the RTC Control register. This register also includes the EHSS bit, which determines whether the sample rate is speci- fied in seconds or minutes. Bit 1: Enable High-Speed Sample (EHSS). This bit controls the speed of the sample rate counter. When set to logic 0, the sample rate is specified in minutes. When set to logic 1, the sample rate is specified in seconds. Temperature Sensor Control Register Bitmap ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 0210h 0 0 0 0 0 0 ETHA ETLA RTC Control Register Bitmap ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 0212h 0 0 0 0 0 0 EHSS EOSC Note: During a mission, there is only read access to this register. Bits 2 to 7 have no function. They always read 0 and cannot be written to 1. Note: During a mission, there is only read access to this register. Bits 2 to 7 have no function. They always read 0 and cannot be written to 1. Humidity Sensor Control Register Bitmap ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 0211h 1 1 1 1 1 1 EHHA EHLA Note: During a mission, there is only read access to this register. Bits 2 to 7 have no function. They always read 1 and cannot be written to 0.

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Bit 0: Enable Oscillator (EOSC). This bit controls the crystal oscillator of the RTC. When set to logic 1, the oscillator starts. When written to logic 0, the oscillator stops and the device is in a low-power data-retention mode. This bit must be 1 for normal operation. A Forced Conversion or Start Mission command automati- cally starts the RTC by changing the EOSC bit to logic 1. Mission Control The DS1923 is set up for its operation by writing appro- priate data to its special function registers, which are located in the two register pages. The settings in the Mission Control register determine whether temperature and/or humidity is logged, which format (8 or 16 bits) applies, and whether old data can be overwritten by new data once the data-log memory is full. An addition- al control bit can be set to tell the DS1923 to wait with logging data until a temperature alarm is encountered. Bit 5: Start Mission Upon Temperature Alarm (SUTA). This bit specifies whether a mission begins immediately (includes delayed start) or if a temperature alarm is required to start the mission. If this bit is 1, the device performs an 8-bit temperature conversion at the selected sample rate and begins with data logging only if an alarming temperature (high alarm or low alarm) was found. The first logged temperature is when the alarm occurred. However, the Mission Sample Counter does not increment. The start upon temperature alarm function is only available if temperature logging is enabled (ETL = 1). Bit 4: Rollover Control (RO). This bit controls whether, during a mission, the data-log memory is overwritten with new data or whether data logging is stopped once the data-log memory is full. Setting this bit to 1 enables the rollover and data logging continues at the begin- ning, overwriting previously collected data. If this bit is 0, the logging and conversions stop once the data-log memory is full. However, the RTC continues to run and the MIP bit remains set until the Stop Mission command is performed. Bit 3: Humidity Logging Format Selection (HLFS). This bit specifies the format used to store humidity readings in the data-log memory. If this bit is 0, the data is stored in 8-bit format. If this bit is 1, the 16-bit format is used (higher resolution). With 16-bit format, the most significant byte is stored at the lower address. Bit 2: Temperature Logging Format Selection (TLFS). This bit specifies the format used to store tem- perature readings in the data-log memory. If this bit is 0, the data is stored in 8-bit format. If this bit is 1, the 16-bit format is used (higher resolution). With 16-bit for- mat, the most significant byte is stored at the lower address. Bit 1: Enable Humidity Logging (EHL). To set up the DS1923 for a humidity-logging mission, this bit must be set to logic 1. If temperature and humidity logging are enabled, the recorded humidity values begin at address 2000h (TLFS = HLFS) or 1A00h (TLFS = 0; HLFS = 1) or 2400h (TLFS = 1; HLFS = 0). If only humidity logging is enabled, the recorded values are stored starting at address 1000h. Since humidity data has little scientific value without knowing the tempera- ture, typically both humidity and temperature logging are enabled (i.e., ETL and EHL are set to 1). Bit 0: Enable Temperature Logging (ETL). To set up the device for a temperature-logging mission, this bit must be set to logic 1. To successfully start a mission, ETL or EHL must be 1. If temperature logging is enabled, the recorded temperature values are always stored starting at address 1000h. Mission Control Register Bitmap ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 0213h 1 1 SUTA RO HLFS TLFS EHL ETL Note:During a mission, there is only read access to this register. Bits 6 and 7 have no function. They always read 1 and cannot be written to 0.

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Alarm Status The fastest way to determine whether a programmed temperature or humidity threshold was exceeded during a mission is through reading the Alarm Status register. In a networked environment that contains multiple DS1923 i Buttons, the devices that encountered an alarm can quickly be identified by means of the Conditional Search command (see the 1-Wire ROM Function Commands section). The humidity and temperature alarm only occurs if enabled (see the Temperature Sensor Alarm and Humidity Alarm sections). The BOR alarm is always enabled. Bit 7: Battery-On Reset Alarm (BOR). If this bit reads 1, the device has performed a power-on reset. This indicates that the device has experienced a shock big enough to interrupt the internal battery power supply. The device can still appear functional, but it has lost its factory calibration. Any data found in the data-log memory should be disregarded. Bit 3: Humidity High Alarm Flag (HHF). If this bit reads 1, there was at least one humidity reading during a mission revealing a value equal to or higher than the value in the Humidity High Alarm register. A forced conversion can affect the HHF bit. Bit 2: Humidity Low Alarm Flag (HLF). If this bit reads 1, there was at least one humidity reading during a mis- sion revealing a value equal to or lower than the value in the Humidity Low Alarm register. A forced conversion can affect the HLF bit. Bit 1: Temperature High Alarm Flag (THF). If this bit reads 1, there was at least one temperature conversion during a mission revealing a temperature equal to or higher than the value in the Temperature High Alarm register. A forced conversion can affect the THF bit. This bit can also be set with the initial alarm in the SUTA = 1 mode. Bit 0: Temperature Low Alarm Flag (TLF). If this bit reads 1, there was at least one temperature conversion during a mission revealing a temperature equal to or lower than the value in the Temperature Low Alarm reg- ister. A forced conversion can affect the TLF bit. This bit can also be set with the initial alarm in the SUTA = 1 mode. General Status The information in the General Status register tells the host computer whether a mission-related command was executed successfully. Individual status bits indi- cate whether the DS1923 is performing a mission, wait- ing for a temperature alarm to trigger the logging of data or whether the data from the latest mission has been cleared. Bit 4: Waiting for Temperature Alarm (WFTA). If this bit reads 1, the mission start upon temperature alarm was selected and the Start Mission command was suc- cessfully executed, but the device has not yet experi- enced the temperature alarm. This bit is cleared after a temperature alarm event, but is not affected by the Clear Memory command. Once set, WFTA remains set if a mission is stopped before a temperature alarm occurs. To clear WFTA manually before starting a new mission, set the high temperature alarm (address 0209h) to -40°C and perform a forced conversion. Bit 3: Memory Cleared (MEMCLR). If this bit reads 1, the Mission Timestamp, Mission Samples Counter, and all the alarm flags of the Alarm Status register have been cleared in preparation of a new mission. Executing the Clear Memory command clears these memory sections. The MEMCLR bit returns to 0 as soon as a new mission is started by using the Start Mission command. The memory must be cleared for a mission to start. Bit 1: Mission in Progress (MIP). If this bit reads 1, the device has been set up for a mission and this mission is still in progress. The MIP bit returns from logic 1 to logic 0 when a mission is ended. See the Start Mission with Password and Stop Mission with Passwordsections. Alarm Status Register Bitmap ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 0214h BOR 1 1 1 HHF HLF THF TLF General Status Register Bitmap ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 0215h 1 1 0 WFTA MEMCLR 0 MIP 0 Note: There is only read access to this register. Bits 4 to 6 have no function. They always read 1. All five alarm status bits are cleared simultaneously when the Clear Memory command is invoked. See the Memory and Control Functions section for details. Note: There is only read access to this register. Bits 0, 2, 5, 6, and 7 have no function.

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Mission Samples Counter Register Bitmap ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 0220h Low Byte 0221h Center Byte 0222h High Byte Mission Timestamp Register Bitmap ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 0219h 0 10 Seconds Single Seconds 021Ah 0 10 Minutes Single Minutes 021Bh 0 12/24 20 Hours AM/PM 10 Hours Single Hours 021Ch 0 0 10 Date Single Date 021Dh CENT 0 0 10 Months Single Months 021Eh 10 Years Single Years Mission Start Delay The content of the Mission Start Delay Counter register tells how many minutes must expire from the time a mis- sion was started until the first measurement of the mis- sion takes place (SUTA = 0) or until the device starts testing the temperature for a temperature alarm (SUTA = 1). The Mission Start Delay register is stored as an unsigned 24-bit integer number. The maximum delay is 16,777,215min, equivalent to 11,650 days or roughly 31yr. If the start delay is nonzero and the SUTA bit is set to 1, first the delay must expire before the device starts testing for temperature alarms to begin logging data. For a typical mission, the Mission Start Delay is 0. If a mission is too long for a single DS1923 to store all read- ings at the selected sample rate, one can use several devices and set the Mission Start Delay for the second device to start recording as soon as the memory of the first device is full, and so on. The RO bit in the Mission Control register (address 0213h) must be set to 0 to prevent overwriting of collected data once the data-log memory is full. Mission Timestamp The Mission Timestamp register indicates the date and time of the first temperature and humidity sample of the mission. There is only read access to the Mission Timestamp register. Mission Progress Indicator Depending on settings in the Mission Control register (address 0213h), the DS1923 logs temperature and/or humidity in 8-bit or 16-bit format. The description of the ETL and EHL bit explains where the device stores data in its data-log memory. The Mission Samples Counter register together with the starting address and the log- ging format (8 or 16 bits) provide the information to iden- tify valid blocks of data that have been gathered during the current (MIP = 1) or latest mission (MIP = 0). See the Data-Log Memory Usage section for an illustration. Note that when SUTA = 1, the Mission Samples Counter does not increment when the first sample is logged. The number read from the Mission Samples Counter indi- cates how often the DS1923 woke up during a mission to measure temperature and/or humidity. The number for- mat is 24-bit unsigned integer. The Mission Samples Counter is reset through the Clear Memory command. Note: There is only read access to this register. Note that when both the internal temperature and humidity logging are enabled, the two log readings are counted as one event in the Mission Sample Counter and Device Sample Counter. Note: There is only read access to this register. Mission Start Delay Counter Register Bitmap ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 0216h Delay Low Byte 0217h Delay Center Byte 0218h Delay High Byte Note: During a mission, there is only read access to this register.

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Other Indicators The Device Samples Counter register is similar to the Mission Samples Counter register. During a mission this counter increments whenever the DS1923 wakes up to measure and log data and when the device is testing for a temperature alarm in SUTA mode. Between mis- sions, the counter increments whenever the Forced Conversion command is executed. This way the Device Samples Counter register functions like a gas gauge for the battery that powers the i Button. The Device Samples Counter register is reset to zero when the iButton is assembled. The counter increments a couple of times during final test. The number format is 24-bit unsigned integer. The maximum number that can be represented in this format is 16,777,215. The code in the Device Configuration register allows the master to distinguish between the DS2422 chip and dif- ferent versions of the DS1922 i Buttons. The Device Configuration Register table shows the codes assigned to the various devices. Security by Password The DS1923 is designed to use two passwords that control read access and full access. Reading from or writing to the scratchpad as well as the Forced Conversion command does not require a password. The password must be transmitted immediately after the command code of the memory or control function. If password checking is enabled, the password transmit- ted is compared to the passwords stored in the device. The data pattern stored in the Password Control regis- ter determines whether password checking is enabled. To enable password checking, the EPW bits need to form a binary pattern of 10101010 (AAh). The default pattern of EPW is different from AAh. If the EPW pattern is different from AAh, any pattern is accepted as long as it has a length of exactly 64 bits. Once enabled, changing the passwords and disabling password checking requires the knowledge of the current full- access password. Device Samples Counter Register Bitmap ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 0223h Low Byte 0224h Center Byte 0225h High Byte Password Control Register Bitmap ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 0227h EPW Device Configuration Register Bitmap ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 PART 0 0 0 0 0 0 0 0 DS2422 0 0 1 0 0 0 0 0 DS1923 0 1 0 0 0 0 0 0 DS1922L 0 1 1 0 0 0 0 0 DS1922T 0226h 1 0 0 0 0 0 0 0 DS1922E Note: There is only read access to this register. Note: There is only read access to this register. Note: During a mission, there is only read access to this register.

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Before enabling password checking, passwords for read-only access as well as for full access (read/write/control) must be written to the password registers. Setting up a password or enabling/dis- abling the password checking is done in the same way as writing data to a memory location; only the address is different. Since they are located in the same memory page, both passwords can be rede- fined at the same time. The Read Access Password must be transmitted exact- ly in the sequence RP0, RP1…RP62, RP63. This pass- word only applies to the Read Memory with CRC command. The DS1923 delivers the requested data only if the password transmitted by the master was cor- rect or if password checking is not enabled. The Full Access Password must be transmitted exactly in the sequence FP0, FP1…FP62, FP63. It affects the commands Read Memory with CRC, Copy Scratchpad, Clear Memory, Start Mission, and Stop Mission. The DS1923 executes the command only if the password transmitted by the master was correct or if password checking is not enabled. Due to the special behavior of the write-access logic, the Password Control register and both passwords must be written at the same time. When setting up new passwords, always verify (read back) the scratchpad before sending the Copy Scratchpad command. After a new password is successfully copied from the scratch- pad to its memory location, erase the scratchpad by fill- ing it with new data (Write Scratchpad command). Otherwise, a copy of the passwords remains in the scratchpad for public read access. Read-Access Password Register Bitmap ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 0228h RP7 RP6 RP5 RP4 RP3 RP2 RP1 RP0 0229h RP15 RP14 RP13 RP12 RP11 RP10 RP9 RP8 … … 022Eh RP55 RP54 RP53 RP52 RP51 RP50 RP49 RP48 022Fh RP63 RP62 RP61 RP60 RP59 RP58 RP57 RP56 Full-Access Password Register Bitmap ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 0230h FP7 FP6 FP5 FP4 FP3 FP2 FP1 FP0 0231h FP15 FP14 FP13 FP12 FP11 FP10 FP9 FP8 … … 0236h FP55 FP54 FP53 FP52 FP51 FP50 FP49 FP48 0237h FP63 FP62 FP61 FP60 FP59 FP58 FP57 FP56 Note: There is only write access to this register. Attempting to read the password reports all zeros. The password cannot be changed while a mission is in progress. Note: There is only write access to this register. Attempting to read the password reports all zeros. The password cannot be changed while a mission is in progress.

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Data-Log Memory Usage Once set up for a mission, the DS1923 logs the temper- ature and/or humidity measurements at equidistant time points entry after entry in its data-log memory. The data-log memory can store 8192 entries in 8-bit format or 4096 entries in 16-bit format (Figure 7a). If tempera- ture as well as humidity are logged, both in the same format, the memory is split into two equal sections that can store 4096 8-bit entries or 2048 16-bit entries (Figure 7b). If the device is set up to log data in differ- ent formats, e. g., temperature in 8-bit and humidity in 16-bit format, the memory is split into blocks of different size, accommodating 2560 entries for either data source (Figure 7c). In this case, the upper 256 bytes are not used. In 16-bit format, the higher 8 bits of an entry are stored at the lower address. Knowing the starting time point (Mission Timestamp) and the interval between temperature measurements, one can recon- struct the time and date of each measurement. There are two alternatives to the way the DS1923 behaves after the data-log memory is filled with data. The user can program the device to either stop any fur- ther recording (disable rollover) or overwrite the previ- ously recorded data (enable rollover), one entry at a time, starting again at the beginning of the respective memory section. The contents of the Mission Samples Counter in conjunction with the sample rate and the Mission Timestamp allow reconstructing the time points of all values stored in the data-log memory. This gives the exact history over time for the most recent measurements taken. Earlier measurements cannot be reconstructed. Missioning The typical task of the DS1923 iButton is recording tem- perature and/or humidity. Before the device can per- form this function, it needs to be set up properly. This procedure is called missioning. First, the DS1923 must have its RTC set to a valid time and date. This reference time can be the local time, or, when used inside of a mobile unit, UTC (also called GMT, Greenwich Mean Time), or any other time stan- dard that was agreed upon. The RTC oscillator must be running (EOSC = 1). The memory assigned to store the Mission Timestamp, Mission Samples Counter, and alarm flags must be cleared using the Memory Clear command. To enable the device for a mission, at least one of the enable logging bits (ETL, EHL) must be set to 1. These are general settings that must be made in any case, regardless of the type of object to be moni- tored and the duration of the mission. If alarm signaling is desired, the temperature alarm and/or humidity alarm low and high thresholds must be defined. See the Temperature Conversion section for information on how to convert a temperature value into the binary code to be written to the threshold registers. See the Humidity Conversion section for information on determining the thresholds for the humidity alarm. In addition, the temperature alarm and/or humidity alarm must be enabled for the low and/or high threshold. This makes the device respond to a Conditional Search command (see the 1-Wire ROM Function Commands section), provided that an alarming condition has been encountered. The setting of the RO bit (rollover enable) and sample rate depends on the duration of the mission and the monitoring requirements. If the most recently logged data is important, the rollover should be enabled (RO = 1). Otherwise one should estimate the duration of the mission in minutes and divide the number by 8192 (sin- gle channel 8-bit format) or 4096 (single channel 16-bit format, two channels 8-bit format) or 2048 (two channels 16-bit format) or 2560 (two channels, one 8-bit and one 16-bit format) to calculate the value of the sample rate (number of minutes between conversions). If the esti- mated duration of a mission is 10 days (= 14400min), for example, then the 8192-byte capacity of the data-log memory would be sufficient to store a new 8-bit value every 1.8min (110s). If the data-log memory of the DS1923 is not large enough to store all readings, one can use several devices and set the Mission Start Delay to values that make the second device start logging as soon as the memory of the first device is full, and so on. The RO-bit needs to be set to 0 to disable rollover that would otherwise overwrite the logged data. After the RO bit and the Mission Start Delay are set, the sample rate must be written to the Sample Rate regis- ter. The sample rate can be any value from 1 to 16,383, coded as an unsigned 14-bit binary number. The fastest sample rate is one sample per second (EHSS = 1, sample rate = 0001h) and the slowest is one sample every 273.05hr (EHSS = 0, sample rate = 3FFFh). To get one sample every 6min, for example, the sample rate value must be set to 6 (EHSS = 0) or 360 decimal (equivalent to 0168h at EHSS = 1). If there is a risk of unauthorized access to the DS1923 or manipulation of data, one should define passwords for read access and full access. Before the passwords become effective, their use must be enabled. See the Security by Password section for more details.

Sample Rate register and the EHSS bit. 1), the DS1923 first waits until the start delay is over. ple period later the Mission Timestamp register is set. at any time, e.g., to watch the progress of a mission. of the data that is stored in the password registers. Figure 8. Address Registers

efficiency, the target address for writing should point to the beginning of a page, i.e., the byte offset is 0. Thus, the full 32-byte capacity of the scratchpad is available, resulting also in the ending offset of 1Fh. The ending offset together with the PF flag are a means to support the master checking the data integrity after a Write command. The highest valued bit of the E/S register, called authorization accepted (AA), indicates that a valid Copy command for the scratchpad has been received and executed. Writing data to the scratchpad clears this flag. Writing with Verification To write data to the DS1923, the scratchpad must be used as intermediate storage. First, the master issues the Write Scratchpad command to specify the desired target address, followed by the data to be written to the scratchpad. In the next step, the master sends the Read Scratchpad command to read the scratchpad and to verify data integrity. As preamble to the scratch- pad data, the DS1923 sends the requested target address TA1 and TA2 and the contents of the E/S Register. If the PF flag is set, data did not arrive cor- rectly in the scratchpad. The master does not need to continue reading; it can start a new trial to write data to the scratchpad. Similarly, a set AA flag indicates that the Write command was not recognized by the device. If everything went correctly, both flags are cleared and the ending offset indicates the address of the last byte written to the scratchpad. Now the master can continue verifying every data bit. After the master has verified the data, it must send the Copy Scratchpad command. This command must be followed exactly by the data of the three address registers TA1, TA2, and E/S, as the master has read them verifying the scratchpad. As soon as the DS1923 has received these bytes, it copies the data to the requested location beginning at the tar- get address. Memory and Control Function Commands Figure 9 shows the protocols necessary for accessing the memory and the special function registers of the DS1923. An example on how to use these and other functions to set up the DS1923 for a mission is included in the Mission Example: Prepare and Start a New Mission section. The communication between the mas- ter and the DS1923 takes place either at standard speed (default, OD = 0) or at overdrive speed (OD = 1). If not explicitly set into the overdrive mode, the DS1923 assumes standard speed. Internal memory access during a mission has priority over external access through the 1-Wire interface. This affects sever- al commands in this section. See the Memory Access Conflicts section for details and solutions. Write Scratchpad [0Fh] After issuing the Write Scratchpad command, the mas- ter must first provide the 2-byte target address, fol- lowed by the data to be written to the scratchpad. The data is written to the scratchpad starting at the byte off- set T[4:0]. The master must send as many bytes as are needed to reach the ending offset of 1Fh. If a data byte is incomplete, its content is ignored and the partial byte flag PF is set. When executing the Write Scratchpad command, the CRC generator inside the DS1923 calculates a CRC of the entire data stream, starting at the command code and ending at the last data byte sent by the master (Figure 15). This CRC is generated using the CRC-16 polynomial by first clearing the CRC generator and then shifting in the command code (0Fh) of the Write Scratchpad command, the target addresses TA1 and TA2 as supplied by the master, and all the data bytes. If the ending offset is 11111b, the master can send 16 read time slots and receive the inverted CRC-16 gener- ated by the DS1923. Note that both register pages are write protected dur- ing a mission. Although the Write Scratchpad command works normally at any time, the subsequent copy scratchpad to a register page fails during a mission. DS1923 Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory

Figure 8. The master can continue reading data until until a reset pulse is issued. successful. The AA bit remaining at 0 indicates this. 2-byte address that indicates a starting byte location. continuing until the end of a 32-byte page is reached. data time slots and receives the inverted 16-bit CRC. memory page followed again by the CRC for that page.

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory MASTER Tx MEMORY OR CONTROL FUNCTION COMMAND MASTER Tx TA1 [T7:T0] MASTER Tx DATA BYTE TO SCRATCHPAD OFFSET DS1923 INCREMENTS SCRATCHPAD OFFSET DS1923 SETS SCRATCHPAD OFFSET = [T4:T0] AND CLEARS (PF, AA) 0Fh WRITE SCRATCHPAD? N Y Y N Y N N Y N MASTER Tx RESET? SCRATCHPAD OFFSET = 11111b? MASTER Tx RESET? MASTER Tx RESET? MASTER Tx TA2 [T15:T8] DS1923 SETS [E4:E0] = SCRATCHPAD OFFSET N FROM ROM FUNCTIONS FLOWCHART (FIGURE 11) TO ROM FUNCTIONS FLOWCHART (FIGURE 11) Y Y TO FIGURE 9b FROM FIGURE 9b MASTER Rx CRC-16 OF COMMAND, ADDRESS DATA MASTER Rx "1"s PARTIAL BYTE WRITTEN? PF = 1 AA = 1 MASTER Rx TA1 [T7:T0] DS1923 SETS SCRATCHPAD OFFSET = [T4:T0] DS1923 INCREMENTS SCRATCHPAD OFFSET MASTER Rx ENDING OFFSET WITH DATA STATUS (E/S) AAh READ SCRATCHPAD? N Y Y N Y N Y N MASTER Tx RESET? SCRATCHPAD OFFSET = 11111b? MASTER Tx RESET? MASTER Rx TA2 [T15:T8] MASTER Rx DATA BYTE FROM SCRATCHPAD OFFSET MASTER Rx CRC-16 OF COMMAND, ADDRESS DATA, E/S BYTE, AND DATA STARTING AT THE TARGET ADDRESS MASTER Rx "1"s 99h COPY SCRATCHPAD [WITH PW] N Y Y N N MASTER Tx RESET? MASTER Tx RESET? COPYING FINISHED MASTER Tx E/S BYTE MASTER Tx TA1 [T7:T0], TA2 [T15:T8] AUTHORIZATION CODE MASTER Tx

64 BITS [PASSWORD]

N Y AUTHORIZATION CODE MATCH? N Y N Y Y N MASTER Tx RESET? Y PASSWORD ACCEPTED? DS1923 Tx "0" DS1923 Tx "1" MASTER Rx "1"s MASTER Rx "1"s Figure 9a. Memory/Control Function Flowchart

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory FROM FIGURE 9a TO FIGURE 9a TO FIGURE 9c FROM FIGURE 9c 69h READ MEMORY [WITH PW] AND CRC N N Y Y N N END OF MEMORY? MASTER Tx RESET? CRC OK? MASTER Tx TA1 [T7:T0], TA2 [T15:T8] DS1923 SETS MEMORY ADDRESS = [T15:T0] MASTER Rx DATA BYTE FROM MEMORY ADDRESS Y N N N END OF PAGE? DECISION MADE BY MASTER DECISION MADE BY DS1923 Y N Y Y MASTER Tx RESET? Y PASSWORD ACCEPTED? MASTER Tx RESET MASTER Rx "1"s MASTER Rx CRC-16 OF COMMAND, ADDRESS, DATA (1ST PASS); CRC-16 OF DATA (SUBSEQUENT PASSES) DS1923 INCREMENTS ADDRESS COUNTER N Y MASTER Tx FFh DUMMY BYTE MASTER Tx MEMCLR = 1 YMISSION IN PROGRESS? N N Y MASTER Tx RESET? Y PASSWORD ACCEPTED? DS1923 CLEARS MISSION TIMESTAMP, MISSION SAMPLES COUNTER, ALARM FLAGS 96h CLEAR MEMORY [WITH PW] N N Y MASTER Tx FFh DUMMY BYTE DS1923 COPIES RESULT TO ADDRESS 020C/Dh DS1923 PERFORMS A TEMPERATURE CONVERSION DS1923 PERFORMS A HUMIDITY CONVERSION DS1923 COPIES RESULT TO ADDRESS 020E/Fh YMISSION IN PROGRESS? N MASTER Tx RESET? Y 55h FORCED CONVERSION? Figure 9b. Memory/Control Function Flowchart (continued)

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory MISSION START DELAY PROCESS FROM FIGURE 9b TO FIGURE 9b YSTART DELAY COUNTER = 0? N NSUTA = 1? Y NTEMPERATURE ALARM? Y MIP = 0? N N N Y MASTER Tx FFh DUMMY BYTE MASTER Tx DS1923 SETS WFTA = 1 DS1923 SETS WFTA = 0 AND LOGS FIRST SAMPLE THE MISSION SAMPLES COUNTER DOES NOT INCREMENT DS1923 DECREMENTS START DELAY COUNTER DS1923 WAITS ONE SAMPLE PERIOD DS1923 PERFORMS 8-BIT TEMPERATURE CONVERSION DS1923 WAITS ONE SAMPLE PERIOD IF SUTA = 1, THIS IS THE SECOND SAMPLE. MISSION IN PROGRESS? N Y MASTER Tx RESET? Y PASSWORD ACCEPTED? N Y Y MEMCLR = 1? Y N DS1923 SETS MIP = 1, MEMCLR = 0 DS1923 COPIES RTC DATA TO MISSION TIMESTAMP REGISTER DS1923 STARTS LOGGING TAKING FIRST SAMPLE DS1923 INITIATES MISSION START DELAY PROCESS CCh START MISSION [WITH PW] N Y MASTER Tx FFh DUMMY BYTE MASTER Tx PROGRESS? Y Y MASTER Tx RESET? Y PASSWORD ACCEPTED? DS1923 SETS MIP = 0, WFTA = 0 33h STOP MISSION [WITH PW] N N N END OF PROCESS Figure 9c. Memory/Control Function Flowchart (continued)

Clear Memory with Password [96h] The Clear Memory with Password command is used to prepare the device for another mission. This command is only executed if no mission is in progress. After the command code, the master must transmit the 64-bit full-access password followed by an FFh dummy byte. If passwords are enabled and the transmitted pass- word is different from the stored full access password or a mission is in progress, the Clear Memory with Password command fails. The device stops communi- cating and waits for a reset pulse. If the password was correct or if passwords were not enabled, the device clears the Mission Timestamp register, Mission Samples Counter register, and all alarm flags of the Alarm Status register. After these cells are cleared, the MEMCLR bit of the General Status register reads 1 to indicate the successful execution of the Clear Memory with Password command. Clearing of the data-log memory is not necessary because the Mission Samples Counter indicates how many entries in the data-log memory are valid. Forced Conversion [55h] The Forced Conversion command can be used to mea- sure the temperature and humidity without starting a mission. After the command code, the master must send one FFh byte to get the conversion started. The conversion result is found as a 16-bit value in the Latest Temperature Conversion Result and Latest Humidity Conversion Result registers. This command is only exe- cuted if no mission is in progress (MIP = 0). It cannot be interrupted and takes maximum 666ms to complete. During this time memory access through the 1-Wire interface is blocked. The device behaves the same way as during a mission when the sampling interferes with a memory/control function command. See the Memory Access Conflicts section for details. Start Mission with Password [CCh] The DS1923 uses a control function command to start a mission. A new mission can only be started if the previ- ous mission has been ended and the memory has been cleared. After the command code, the master must transmit the 64-bit full access password followed by an FFh dummy byte. If passwords are enabled and the transmitted password is different from the stored full- access password or a mission is in progress, the Start Mission with Password command fails. The device stops communicating and waits for a reset pulse. If the password was correct or if passwords were not enabled, the device starts a mission. If SUTA = 0, the sampling begins as soon as the Mission Start Delay is over. If SUTA = 1, the first sample is written to the data- log memory at the time the temperature alarm occurred. However, the Mission Sample Counter does not increment. One sample period later, the Mission Timestamp register is set and the regular sampling and logging begins. While the device is waiting for a tem- perature alarm to occur, the WFTA flag in the General Status register reads 1. During a mission there is only read access to the register pages. Stop Mission with Password [33h] The DS1923 uses a control function command to stop a mission. Only a mission that is in progress can be stopped. After the command code, the master must transmit the 64-bit full access password followed by a FFh dummy byte. If passwords are enabled and the transmitted password is different from the stored full- access password or a mission is not in progress, the Stop Mission with Password command fails. The device stops communicating and waits for a reset pulse. If the password was correct or if passwords were not enabled, the device clears the MIP bit in the General Status register and restores write access to the register pages. The WFTA bit is not cleared. See the description of the general status register for a method to clear the WFTA bit. Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory

and to take measures to work around it. Table 5. Memory Access Conflicts and Solutions CRC-16 at the end of the command flow. the command flow, despite a valid password. the CRC-16 at the end of the memory page. FFh or the MIP bit is 1 while bits 0, 2, and 5 are 0. is 0, Stop Mission was successful.

boosted to 142kbps by activating the overdrive mode. speed is 15.4kbps and 125kbps in overdrive speed. adapters that are based on these driver chips.

• Initialization
• ROM Function Command
• Memory/Control Function Command
• Transaction/Data Rx RPUP IL VPUP BUS MASTER OPEN-DRAIN PORT PIN 100Ω MOSFET Tx Rx Tx DATA DS1923 1-Wire PORT Rx = RECEIVE Tx = TRANSMIT

Figure 10. Hardware Configuration

All transactions on the 1-Wire bus begin with an initial- ization sequence. The initialization sequence consists of a reset pulse transmitted by the bus master followed by presence pulse(s) transmitted by the slave(s). The presence pulse lets the bus master know that the DS1923 is on the bus and is ready to operate. For more details, see the 1-Wire Signaling section. 1-Wire ROM Function Commands Once the bus master has detected a presence, it can issue one of the eight ROM function commands that the DS1923 supports. All ROM function commands are 8 bits long. A list of these commands follows (see the flowchart in Figure 11). Read ROM [33h] This command allows the bus master to read the DS1923’s 8-bit family code, unique 48-bit serial number, and 8-bit CRC. This command can only be used if there is a single slave on the bus. If more than one slave is pre- sent on the bus, a data collision occurs when all slaves try to transmit at the same time (open drain produces a wired-AND result). The resultant family code and 48-bit serial number results in a mismatch of the CRC. Match ROM [55h] The Match ROM command, followed by a 64-bit ROM sequence, allows the bus master to address a specific DS1923 on a multidrop bus. Only the DS1923 that exact- ly matches the 64-bit ROM sequence responds to the fol- lowing memory function command. All other slaves wait for a reset pulse. This command can be used with a sin- gle device or multiple devices on the bus. Search ROM [F0h] When a system is initially brought up, the bus master might not know the number of devices on the 1-Wire bus or their registration numbers. By taking advantage of the wired-AND property of the bus, the master can use a process of elimination to identify the registration numbers of all slave devices. For each bit of the regis- tration number, starting with the least significant bit, the bus master issues a triplet of time slots. On the first slot, each slave device participating in the search outputs the true value of its registration number bit. On the sec- ond slot, each slave device participating in the search outputs the complemented value of its registration num- ber bit. On the third slot, the master writes the true value of the bit to be selected. All slave devices that do not match the bit written by the master stop participat- ing in the search. If both of the read bits are zero, the master knows that slave devices exist with both states of the bit. By choosing which state to write, the bus master branches in the ROM code tree. After one com- plete pass, the bus master knows the registration num- ber of a single device. Additional passes identify the registration numbers of the remaining devices. Refer to Application Note 187: 1-Wire Search Algorithm for a detailed discussion, including an example. Conditional Search ROM [ECh] The Conditional Search ROM command operates simi- larly to the Search ROM command except that only those devices that fulfill certain conditions participate in the search. This function provides an efficient means for the bus master to identify devices on a multidrop system that have to signal an important event. After each pass of the conditional search that successfully determined the 64-bit ROM code for a specific device on the multidrop bus, that particular device can be indi- vidually accessed as if a Match ROM had been issued, since all other devices have dropped out of the search process and are waiting for a reset pulse. The DS1923 responds to the conditional search ROM command if one of the five alarm flags of the Alarm Status register (address 0214h) reads 1. The humidity and temperature alarm only occurs if enabled (see the Temperature Sensor Alarm and Humidity Alarm sec- tions). The BOR alarm is always enabled. The first alarm that occurs makes the device respond to the Conditional Search ROM command. DS1923 Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory

Skip ROM [CCh] This command can save time in a single-drop bus sys- tem by allowing the bus master to access the memory functions without providing the 64-bit ROM code. For example, if more than one slave is present on the bus and a Read command is issued following the Skip ROM command, data collision occurs on the bus as multiple slaves transmit simultaneously (open-drain pulldowns produce a wired-AND result). Resume [A5h] The DS1923 must be accessed several times before a mission starts. In a multidrop environment this means that the 64-bit ROM code after a Match ROM command must be repeated for every access. To maximize the data throughput in a multidrop environment, the Resume command was implemented. This command checks the status of the RC bit and, if it is set, directly transfers con- trol to the memory/control functions, similar to a Skip ROM command. The only way to set the RC bit is through successfully executing the Match ROM, Search ROM, or Overdrive-Match ROM command. Once the RC bit is set, the device can repeatedly be accessed through the Resume command. Accessing another device on the bus clears the RC bit, preventing two or more devices from simultaneously responding to the Resume command. Overdrive-Skip ROM [3Ch] On a single-drop bus this command can save time by allowing the bus master to access the memory/control functions without providing the 64-bit ROM code. Unlike the normal Skip ROM command, the Overdrive-Skip ROM command sets the DS1923 in the overdrive mode (OD = 1). All communication following this command must occur at overdrive speed until a reset pulse of minimum 690μs duration resets all devices on the bus to standard speed (OD = 0). When issued on a multidrop bus, this command sets all overdrive-supporting devices into overdrive mode. To subsequently address a specific overdrive-supporting device, a reset pulse at overdrive speed must be issued followed by a Match ROM or Search ROM com- mand sequence. This speeds up the time for the search process. If more than one slave supporting overdrive is present on the bus and the Overdrive-Skip ROM command is followed by a Read command, data collision occurs on the bus as multiple slaves transmit simultaneously (open-drain pulldowns produce a wired- AND result). Overdrive-Match ROM [69h] The Overdrive-Match ROM command followed by a 64-bit ROM sequence transmitted at overdrive speed allows the bus master to address a specific DS1923 on a multidrop bus and to simultaneously set it in overdrive mode. Only the DS1923 that exactly matches the 64-bit ROM sequence responds to the subsequent memory/control function command. Slaves already in overdrive mode from a previous Overdrive-Skip ROM or successful Overdrive-Match ROM command remain in overdrive mode. All overdrive-capable slaves return to standard speed at the next reset pulse of minimum 690μs duration. The Overdrive-Match ROM command can be used with a single or multiple devices on the bus. Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory DS1923 Tx PRESENCE PULSE BUS MASTER Tx RESET PULSE BUS MASTER Tx ROM FUNCTION COMMAND DS1923 Tx CRC BYTE DS1923 Tx FAMILY CODE (1 BYTE) DS1923 Tx SERIAL NUMBER (6 BYTES) OD = 0 RC = 0 MASTER Tx BIT 0 RC = 0 RC = 0 RC = 0 Y OD RESET PULSE? YY Y Y Y Y N 33h READ ROM COMMAND? N 55h MATCH ROM COMMAND? BIT 0 MATCH? BIT 0 MATCH? N N N N N N N F0h SEARCH ROM COMMAND? N ECh CONDITIONAL SEARCH COMMAND? N Y RC = 1 MASTER Tx BIT 1 MASTER Tx BIT 63 BIT 1 MATCH? BIT 63 MATCH? Y Y RC = 1 FROM MEMORY/CONTROL FUNCTION FLOWCHART (FIGURE 9) DS1923 Tx BIT 0 DS1923 Tx BIT 0 MASTER Tx BIT 0 BIT 1 MATCH? BIT 63 MATCH? DS1923 Tx BIT 1 DS1923 Tx BIT 1 MASTER Tx BIT 1 DS1923 Tx BIT 63 DS1923 Tx BIT 63 MASTER Tx BIT 63 Y BIT 0 MATCH?N N N Y Y RC = 1 DS1923 Tx BIT 0 DS1923 Tx BIT 0 MASTER Tx BIT 0 CONDITION MET? N Y BIT 1 MATCH? BIT 63 MATCH? DS1923 Tx BIT 1 DS1923 Tx BIT 1 MASTER Tx BIT 1 DS1923 Tx BIT 63 DS1923 Tx BIT 63 MASTER Tx BIT 63 Y FROM FIGURE 11b TO FIGURE 11b TO FIGURE 11b FROM FIGURE 11b TO MEMORY/CONTROL FUNCTION FLOWCHART (FIGURE 9) Figure 11a. ROM Functions Flowchart

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory MASTER Tx BIT 0 RC = 0; OD = 1 RC = 0; OD = 1 OD = 0 (SEE NOTE) NOTE: THE OD FLAG REMAINS AT 1 IF THE DEVICE WAS ALREADY AT OVERDRIVE SPEED BEFORE THE OVERDRIVE-MATCH ROM COMMAND WAS ISSUED. (SEE NOTE) (SEE NOTE) RC = 1? Y N Y A5h RESUME COMMAND? N Y 3Ch OVERDRIVE- SKIP ROM? N RC = 0 Y CCh SKIP ROM COMMAND? Y 69h OVERDRIVE- MATCH ROM? N N OD = 0N OD = 0N MASTER Tx BIT 1 MASTER Tx BIT 63 Y Y RC = 1 Y BIT 0 MATCH? MASTER Tx RESET? BIT 63 MATCH? BIT 1 MATCH? N Y N YMASTER Tx RESET? N TO FIGURE 11a FROM FIGURE 11a FROM FIGURE 11a TO FIGURE 11a Figure 11b. ROM Functions Flowchart (continued)

the fast timing applies to all waveforms. and the capacitance of the 1-Wire network attached. determining a logical level, not triggering any events. than 80μs, the device remains in overdrive mode. must test the logical state of the 1-Wire line at tMSP. write and read time slots are illustrated in Figure 13. Figure 12. Initialization Procedure: Reset and Presence Pulse

For a write-one time slot, the voltage on the data line must have crossed the VTH threshold before the write-one low time tW1LMAX is expired. For a write-zero time slot, the voltage on the data line must stay below the V TH threshold until the write-zero low time tW0LMIN is expired. The voltage on the data line should not exceed V ILMAX during the entire t W0L or t W1L window. After the V TH threshold has been crossed, the DS1923 needs a recov- ery time t REC before it is ready for the next time slot. Slave-to-Master A read-data time slot begins like a write-one time slot. The voltage on the data line must remain below V TL until the read low time t RL is expired. During the t RL window, when responding with a 0, the DS1923 starts pulling the data line low; its internal timing generator determines when this pulldown ends and the voltage starts rising again. When responding with a 1, the DS1923 does not hold the data line low at all, and the voltage starts rising as soon as t RL is over. The sum of tRL + δ (rise time) on one side and the inter- nal timing generator of the DS1923 on the other side define the master sampling window (t MSRMIN to tMSRMAX) in which the master must perform a read from the data line. For most reliable communication, t RL should be as short as permissible and the master should read close to but no later than t MSRMAX. After reading from the data line, the master must wait until t SLOT is expired. This guarantees sufficient recovery time tREC for the DS1923 to get ready for the next time slot. Improved Network Behavior (Switchpoint Hysteresis) In a 1-Wire environment, line termination is possible only during transients controlled by the bus master (1- Wire driver). 1-Wire networks, therefore, are susceptible to noise of various origins. Depending on the physical size and topology of the network, reflections from end points and branch points can add up or cancel each other to some extent. Such reflections are visible as glitches or ringing on the 1-Wire communication line. Noise coupled onto the 1-Wire line from external sources can also result in signal glitching. A glitch dur- ing the rising edge of a time slot can cause a slave device to lose synchronization with the master and, as a consequence, result in a search ROM command coming to a dead end or cause a device-specific func- tion command to abort. For better performance in net- work applications, the DS1923 uses a new 1-Wire front-end, which makes it less sensitive to noise and also reduces the magnitude of noise injected by the slave device itself. The DS1923’s 1-Wire front-end differs from traditional slave devices in four characteristics: 1) The falling edge of the presence pulse has a con- trolled slew rate. This provides a better match to the line impedance than a digitally switched transistor, converting the high-frequency ringing known from traditional devices into a smoother, low-bandwidth transition. The slew-rate control is specified by the parameter t FPD, which has different values for stan- dard and overdrive speed. 2) There is additional lowpass filtering in the circuit that detects the falling edge at the beginning of a time slot. This reduces the sensitivity to high-frequency noise. This additional filtering does not apply at over- drive speed. 3) There is a hysteresis at the low-to-high switching threshold V TH. If a negative glitch crosses V TH but does not go below V TH - V HY, it is not recognized (Figure 14, Case A). The hysteresis is effective at any 1-Wire speed. 4) There is a time window specified by the rising edge hold-off time t REH during which glitches are ignored, even if they extend below V TH - V HY threshold (Figure 14, Case B, t GL < t REH ). Deep voltage droops or glitches that appear late after crossing the V TH threshold and extend beyond the t REH window cannot be filtered out and are taken as the begin- ning of a new time sl ot (Figure 14, Case C, t GL ≥ tREH). Devices that have the parameters t FPD, VHY, and t REH specified in their electrical characteristics use the improved 1-Wire front-end. Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory

Figure 13. Read/Write Timing Diagrams

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory ing in the command code, the target addresses TA1 and TA2, and all the data bytes. The DS1923 transmits this CRC only if the data bytes written to the scratchpad include scratchpad ending offset 11111b. The data can start at any location within the scratchpad. With the Read Scratchpad command, the CRC is gen- erated by first clearing the CRC generator and then shifting in the command code, the target addresses TA1 and TA2, the E/S byte, and the scratchpad data starting at the target address. The DS1923 transmits this CRC only if the reading continues through the end of the scratchpad, regardless of the actual ending off- set. For more information on generating CRC values, refer to Application Note 27. Command-Specific 1-Wire Communication Protocol—Legend SYMBOL DESCRIPTION RST 1-Wire reset pulse generated by master. PD 1-Wire presence pulse generated by slave. Select Command and data to satisfy the ROM function protocol. WS Command “Write Scratchpad.” RS Command “Read Scratchpad.” CPS Command “Copy Scratchpad with Password.” RMC Command “Read Memory with Password and CRC.” CM Command “Clear Memory with Password.” FC Command “Forced Conversion.” SM Command “Start Mission with Password.” STP Command “Stop Mission with Password.” TA Target Address TA1, TA2. TA–E/S Target Address TA1, TA2 with E/S byte. <Data to EOS> Transfer of as many data bytes as are needed to reach the scratchpad offset 1Fh. <Data to EOP> Transfer of as many data bytes as are needed to reach the end of a memory page. <Data to EOM> Transfer as many bytes as are needed to reach the end of the data-log memory. <PW/Dummy> Transfer of 8 bytes that either represent a valid password or acceptable dummy data. <32 Bytes> Transfer of 32 bytes. <Data> Transfer of an undetermined amount of data. FFh Transmission of one FFh byte. CRC-16 Transfer of an inverted CRC-16. FF Loop Indefinite loop where the master reads FF bytes. AA Loop Indefinite loop where the master reads AA bytes.

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory RST Write Scratchpad, Reaching the End of the Scratchpad (Cannot Fail) PD WS TASelect CRC-16 FF Loop<Data to EOS> CRC-16 FF Loop CRC-16 RST Read Scratchpad (Cannot Fail) PD RS TA-E/SSelect <Data to EOS> AA LoopRST Copy Scratchpad with Password (Success) PD CPS TA-E/SSelect <PW/Dummy> FF Loop FF Loop Loop RST Copy Scratchpad with Password (Fail TA-E/S or Password) PD CPS TA-E/SSelect <PW/Dummy> FF Loop FF Loop RST Read Memory with Password and CRC (Fail Password or Address) PD RMC FFh Select <PW/Dummy> RST TA TA Read Memory with Password and CRC (Success) PD RMCSelect <PW/Dummy> <Data to EOP> RST CM Clear Memory with Password PD Select <PW/Dummy> CRC-16<32 Bytes> To verify success, read the General Status register at address 0215h. If MEMCLR is 1, the command was executed successfully. Command-Specific 1-Wire Communication Protocol—Color Codes Master-to-Slave Slave-to-Master 1-Wire Communication Examples

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Mission Example: Prepare and Start a New Mission Assumption: The previous mission has been ended by using the Stop Mission command. Passwords are not enabled. The device is a DS1923. Starting a mission requires three steps: Step 1: Clear the data of the previous mission. Step 2: Write the setup data to register page 1. Step 3: Start the new mission. Step 1: Clear the data of the previous mission. With only a single device connected to the bus master, the communication of step 1 looks like this: RST Forced Conversion PD FCSelect FF LoopFFh To read the result and to verify success, read the addresses 020Ch to 020Fh (results) and the Device Samples Counter at address 0223h to 0225h. If the count has incremented, the command was executed successfully. FF LoopRST Start Mission with Password PD SMSelect <PW/Dummy> FFh To verify success, read the General Status register at address 0215h. If MIP is 1 and MEMCLR is 0, the command was executed successfully. RST Stop Mission with Password PD STPSelect FF Loop<PW/Dummy> FFh To verify success, read the General Status register at address 0215h. If MIP is 0, the command was executed successfully. 1-Wire Communication Examples (continued) MASTER MODE DATA (LSB FIRST) COMMENTS Tx (Reset) Reset pulse Rx (Presence) Presence pulse Tx CCh Issue “Skip ROM” command Tx 96h Issue “Clear Memory” command Tx <8 FFh bytes> Send dummy password Tx FFh Send dummy byte Tx (Reset) Reset pulse Rx (Presence) Presence pulse

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Step 2: Write the setup data to register page 1. During the setup, the device needs to learn the follow- ing information:

• Time and Date
• Sample Rate
• Alarm Thresholds
• Alarm Controls (Response to Conditional Search)
• General Mission Parameters (e.g., Channels to Log and Logging Format, Rollover, Start Mode)
• Mission Start Delay The following data sets up the DS1923 for a mission that logs temperature and humidity using 8-bit format for both. ADDRESS DATA EXAMPLE VALUES FUNCTION 0200h 00h 0201h 30h 0202h 15h 15:30:00 hours Time 0203h 15h 0204h 05h 0205h 04h 15th of May in 2004 Date 0206h 0Ah 0207h 00h Every 10 minutes (EHSS = 0) Sample rate 0208h 66h 0209h 7Ah 10°C Low 20°C High Temperature Alarm Thresholds 020Ah 6Fh 020Bh 9Eh 40%RH Low 70%RH High Humidity Alarm Threshold, no software correction used 020Ch FFh 020Dh FFh 020Eh FFh 020Fh FFh (Don’t care) Clock through read-only registers 0210h 03h Enable high and low alarm Temperature Alarm Control 0211h FFh Enable high and low alarm Humidity Alarm Control 0212h 01h On (enabled), EHSS = 0 (low sample rate) RTC Oscillator Control, sample rate selection 0213h C3h Normal start; no rollover; 8-bit logging General Mission Control 0214h FFh 0215h FFh (Don’t care) Clock through read-only registers 0216h 5Ah 0217h 00h 0218h 00h 90 minutes Mission Start Delay

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory With only a single device connected to the bus master, the communication of step 2 looks like this: MASTER MODE DATA (LSB FIRST) COMMENTS Tx (Reset) Reset pulse Rx (Presence) Presence pulse Tx CCh Issue “Skip ROM” command Tx 0Fh Issue “Write Scratchpad” command Tx 00h TA1, beginning offset = 00h Tx 02h TA2, address = 02 00h Tx <25 Data Bytes> Write 25 bytes of data to scratchpad Tx <7 FFh Bytes> Write through the end of the scratchpad Tx (Reset) Reset pulse Rx (Presence) Presence pulse Tx CCh Issue “Skip ROM” command Tx AAh Issue “Read Scratchpad” command Rx 00h Read TA1, beginning offset = 00h Rx 02h Read TA2, address = 02 00h Rx 1Fh Read E/S, ending offset = 1Fh, flags = 0h Rx <32 Data Bytes> Read scratchpad data and verify Tx (Reset) Reset pulse Rx (Presence) Presence pulse Tx CCh Issue “Skip ROM” command Tx 99h Issue “Copy Scratchpad” command Tx 00h TA1 Tx 02h TA2 Tx 1Fh E/S (AUTHORIZATION CODE) Tx <8 FFh Bytes> Send dummy password Tx (Reset) Reset pulse Rx (Presence) Presence pulse MASTER MODE DATA (LSB FIRST) COMMENTS Tx (Reset) Reset pulse Rx (Presence) Presence pulse Tx CCh Issue “Skip ROM” command Tx CCh Issue “Start Mission” command Tx <8 FFh Bytes> Send dummy password Tx FFh Send dummy byte Tx (Reset) Reset pulse Rx (Presence) Presence pulse Step 3: Start the new mission. With only a single device connected to the bus master, the communication of step 3 looks like this: If step 3 was successful, the MIP bit in the General Status register is 1, the MEMCLR bit is 0, and the Mission Start Delay counts down.

Software Correction Algorithm for Temperature The accuracy of high-resolution temperature conver- sion results (forced conversion as well as temperature logs) can be improved through a correction algorithm. The data needed for this software correction is stored in the calibration memory (memory page 18). It consists of reference temperature (Tr) and conversion result (Tc) for two different temperatures, as shown below. See the Temperature Conversion section for the binary number format. The software correction algorithm requires two addition- al values, which are not stored in the device. For the DS1923 these values are Tr1 = 60°C and Offset = 41. The correction algorithm consists of two steps, prepara- tion and execution. The preparation step first converts temperature data from binary to decimal °C format. Next, three coefficients A, B, and C are computed. In the execution step, the temperature reading as deliv- ered by the DS1923 is first converted from the low/high- byte format (TcL, TcH) to °C (Tc) and then corrected to Tcorr. Once step 1 is performed, the three coefficients can be used repeatedly to correct any temperature reading and temperature log of the same device. Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory ADDRESS DESIGNATOR DESCRIPTION 0240h Tr2H Cold reference temperature, high-byte. 0241h Tr2L Cold reference temperature, low-byte. 0242h Tc2H Conversion result at cold reference temperature, high-byte. 0243h Tc2L Conversion result at cold reference temperature, low-byte. 0244h Tr3H Hot reference temperature, high-byte. 0245h Tr3L Hot reference temperature, low-byte. 0246h Tc3H Conversion result at hot reference temperature, high-byte. 0247h Tc3L Conversion result at hot reference temperature, low-byte. Step 1: Preparation Tr1 = 60 Offset = 41 Tr2 = Tr2H/2 + Tr2L/512 - Offset (convert from binary to °C) Tr3 = Tr3H/2 + Tr3L/512 - Offset (convert from binary to °C) Tc2 = Tc2H/2 + Tc2L/512 - Offset (convert from binary to °C) Tc3 = Tc3H/2 + Tc3L/512 - Offset (convert from binary to °C) Err2 = Tc2 - Tr2 Err3 = Tc3 - Tr3 Err1 = Err2 B = (Tr2 2 - Tr12) x (Err3 - Err1)/[(Tr22 - Tr12) x (Tr3 - Tr1) + (Tr32 - Tr12) x (Tr1 - Tr2)] A = B x (Tr1 - Tr2)/(Tr22 - Tr12) C = Err1 - A x Tr12 - B x Tr1 Step 2: Execution Tc = TcH/2 + TcL/512 - Offset (convert from binary to °C) Tcorr = Tc - (A x Tc 2 + B x Tc + C) (the actual correction)

Software Correction Algorithm for Humidity The accuracy of humidity conversion results (forced conversion as well as logged data) can be improved through a correction algorithm. The data needed for this software correction is stored in the calibration memory (memory page 18). It consists of reference humidity (Hr) and conversion result (Hc) for three differ- ent humidity levels, as shown below. The data is taken at 25°C. The correction algorithm consists of two steps: prepara- tion and execution. The preparation step first converts humidity data from binary to decimal %RH format. Next, three coefficients A, B, and C are computed. In the exe- cution step the humidity reading as delivered by the DS1923 (raw data) is first converted from the low/high- byte format (HcL, HcH) to %RH (Hc) and then correct- ed to Hcorr. Once step 1 is performed, the three coefficients can be used repeatedly to correct any humidity reading and humidity log of the same device. DS1923 Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Numerical Temperature Correction Example CONVERTED DATA FROM CALIBRATION MEMORY ERROR VALUES Tr2 = -10.1297°C Tr3 = 24.6483°C Tc2 = -10.0625°C Tc3 = 24.5°C Err2 = 0.0672°C Err3 = -0.1483°C Err1 = Err2 RESULTING CORRECTION COEFFICIENTS APPLICATION OF CORRECTION COEFFICIENTS TO SAMPLE READING B = -0.008741 A = 0.000175/°C C = -0.039332°C Tc = 22.500000°C Tcorr = 22.647275°C Note: The software correction requires floating point arithmetic (24-bit or better). Suitable math libraries for microcontrollers are found on various websites and are included in cross-compilers. ADDRESS DESIGNATOR DESCRIPTION 0248h Hr1H Low reference humidity, high byte. 0249h Hr1L Low reference humidity, low byte. 024Ah Hc1H Conversion result at low reference humidity, high byte. 024Bh Hc1L Conversion result at low reference humidity, low byte. 024Ch Hr2H Medium reference humidity, high byte. 024Dh Hr2L Medium reference humidity, low byte. 024Eh Hc2H Conversion result at medium reference humidity, high byte. 024Fh Hc2L Conversion result at medium reference humidity, low byte. 0250h Hr3H High reference humidity, high byte. 0251h Hr3L High reference humidity, low byte. 0252h Hc3H Conversion result at high reference humidity, high byte. 0253h Hc3L Conversion result at high reference humidity, low byte.

Step 1: Preparation For the humidity data in the calibration memory, the lower 4 bits of each low byte are set to 0. This simplifies the con- version from the binary data format to raw %RH values to a one-line equation. Hr1 = ((Hr1H x 256 + Hr1L) x 5.02/65536 - 0.958)/0.0307 (convert from binary to %RH) Hr2 = ((Hr2H x 256 + Hr2L) x 5.02/65536 - 0.958)/0.0307 Hr3 = ((Hr3H x 256 + Hr3L) x 5.02/65536 - 0.958)/0.0307 Hc1 = ((Hc1H x 256 + Hc1L) x 5.02/65536 - 0.958)/0.0307 Hc2 = ((Hc2H x 256 + Hc2L) x 5.02/65536 - 0.958)/0.0307 Hc3 = ((Hc3H x 256 + Hc3L) x 5.02/65536 - 0.958)/0.0307 Err1 = Hc1 - Hr1 Err2 = Hc2 - Hr2 Err3 = Hc3 - Hr3 B = [(Hr2 2 - Hr12) x (Err3 - Err1) + Hr32 x (Err1 - Err2) + Hr12 x (Err2 - Err1)]/[(Hr22 - Hr12) x (Hr3 - Hr1) + (Hr32 - Hr12) x (Hr1 - Hr2)] A = [Err2 - Err1 + B x (Hr1 - Hr2)]/(Hr22 - Hr12) C = Err1 - A x Hr12 - B x Hr1 Step 2: Execution Hc = ((HcH x 256 + HcL) x 5.02/65536 - 0.958)/0.0307 (convert from binary to %RH) Hcorr = Hc - (A x Hc 2 + B x Hc + C) (the actual correction) Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Numerical Humidity Correction Example CONVERTED DATA FROM CALIBRATION MEMORY ERROR VALUES Hr1 = 20%RH Hr2 = 60%RH Hr3 = 90%RH Hc1 = 17.65%RH Hc2 = 56.41%RH Hc3 = 89.57%RH Err1 = -2.35%RH Err2 = -3.59%RH Err3 = -0.43%RH RESULTING CORRECTION COEFFICIENTS APPLICATION OF CORRECTION COEFFICIENTS TO SAMPLE READING B = -0.186810 A = 0.001948%RH C = 0.607143%RH Hc = 8.9%RH Hcorr = 9.8%RH Note: The software correction requires floating point arithmetic (24-bit or better). Suitable math libraries for microcontrollers are found on various websites and are included in cross-compilers.

RH Temperature Compensation The data for the software correction of humidity is taken at 25°C. Since the temperature characteristics of the humidity sensor are known, humidity readings taken at other temperatures can be corrected, provided the temperature at the time of the humidity conversion is also known. Therefore, to obtain the most accurate humidity results, both temperature and humidity should be logged. Temperature compensation uses the following equation: HTcorr = (Hcorr x K + α x (T - 25°C) - β x (T - 25°C) Hcorr is the humidity reading with the software correc- tion algorithm for humidity already applied, as explained in the previous section. The function and val- ues of the other parameters are explained in the table below. DS1923 Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory NAME FUNCTION VALUE T Temperature at the time of humidity conversion. (in °C) K Humidity sensor conversion constant. 0.0307 Linear compensation, enumerator. 0.0035/°C Quadratic compensation, enumerator. 0.000043/°C 2 Linear compensation, denominator. >15°C: 0.00001/°C 15°C: -0.00005/°C Quadratic compensation, denominator. 0.000002/°C 2 SAMPLE INPUT DATA APPLICATION OF CORRECTION COEFFICIENTS TO SAMPLE READING T = 70°C Hcorr = 24.445%RH = 0.00001/°C HTcorr = 30.291% Numerical RH Temperature Compensation Example Software Saturation Drift Compensation Capacitive humidity sensors read higher humidity val- ues than the actual humidity level when they are exposed to a high-humidity environment for an extend- ed time period. The DS1923’s humidity sensor pro- duces readings that are higher than the actual humidity when exposed to humidity levels of about 70%RH and higher. This shift continues to increase while the device remains at 70%RH and above. This effect is called sat- uration drift, or hysteresis. This drift is reversible. Readings return to their regular level when the DS1923 is removed from a high-humidity environment. It is possible to compensate for most of the error intro- duced by the saturation drift by post-processing tem- perature and humidity logs using the equation below, which is based on laboratory tests and curve-fitting techniques. ARH k The average software-corrected and tempera- ture-compensated humidity reading of the k th hour that the device is continuously exposed to 70%RH or higher. T k The average software-corrected temperature reading of the k th hour that the device is continuously exposed to 70%RH or higher. N The number of hours that the device is contin- uously exposed to 70%RH or higher. HTcorr The humidity reading at the end of the N th hour with the software correction algorithm for humidity and temperature compensation already applied. See the Software Correction Algorithm for Humidity and RH Temperature Compensation sections for details. The numbers in the equation are derived from curve fit- ting. They apply to a time scale in hours. HScorr HTcorr ARHk k =− ×× −×0 0156 2 54 0 3502.. . TTkk N −() = 25 1001 /

HScorr = HTcorr - Sum of partial corrections = 93.70207%RH - 3.458875%RH HScorr = 90.24319%RH The data in this example was taken from devices that were exposed for several hours to 90%RH at 25°C in a test chamber. The drift per hour decreases the longer the device is exposed to high humidity. The correction algorithm compensates for the drift reasonably well. For some applications, compensation may not be neces- sary since the error introduced by the saturation is rela- tively small. Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory SAMPLE INPUT DATA (N = 8) APPLICATION OF CORRECTION ALGORITHM k (HOUR) T k (°C) ARH k (%RH) PARTIAL CORRECTIONS (INDIVIDUAL ADDENDS) 1 25.1 91.1 1.024321 2 25.0 92.5 0.751140 3 24.9 92.9 0.544824 4 25.0 93.1 0.393535 5 25.1 93.2 0.283950 6 25.1 93.3 0.205086 7 25.0 93.6 0.148591 8 24.9 93.7 0.107428 HTcorr = 93.70207%RH Sum of partial corrections: 3.458875 Numerical Saturation Drift Compensation Example iBut t o n® . com Hygrochron™ 16.25mm 5.89mm 0.51mm 17.35mm FRONT-SIDE BRANDING GND IO A1 41 000000FBC52B 1-Wire® Hygrochron™ iBut t o n® . com YYWW ZZZ DS1923 - F5 BACK-SIDE BRANDING Pin Configuration PACKAGE TYPE PACKAGE CODE DOCUMENT NO. F5 iButton IB-6HB 21-0266

Package Information

For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.

Hygrochron Temperature/Humidity Logger iButton with 8KB Data-Log Memory Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circu it patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 55 © 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.

Revision History

0 8/04 Initial release. — 1 12/07 Changed bullet from “Hydrophobic Filter Protects Sensor Against Dust, Dirt, Water, and Contaminants” to “Hydrophobic Filter Protects Sensor Against Dust, Dirt, Contaminants, and Water Droplets/Condensation.” Deleted “Application Pending” from UL bullet and safety statement. Added text to the Application section: Note that the initial sealing level of DS1923 achieves IP56. Aging and use conditions can degrade the integrity of the seal over time, so for applications with significant exposure to liquids, sprays, or other similar environments, it is recommended to place the Hygrochron under a shield to protect it. (See www.maxim-ic.com/AN4126 ). The hydrophobic filter may not protect the DS1923 from destruction in the event of full submersion in liquid. 1, 4, 10 2 4/09 Created newer template-style data s heet. All 3 10/09 Deleted the standard part number from the Ordering Information table. 1