MCS3122

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Technical content

 2014 Microchip Technology Inc. DS40001762A-page 1 MCS3122 Features Overview

• Advanced K EELOQ® Technology: - Programmable 32-bit serial number - Programmable 32-bit serial number for seed transmissions - AES-128 block cipher - Programmable 128-bit crypt key - 160/192-bit transmission code length: - 32-bit unencrypted portion - 128-bit encrypted, code hopping portion - 32-bit authorization check (optional)
• Operating Features: - 2.0 to 3.7V operation - Three switch inputs - Seven functions available - One active-low LED drive - Configurable maximum code word
• R F : - Configurable bit rate - Configurable modulation, supporting FSK and OOK - Configurable data modulation, supporting PWM and Manchester
• O t h e r : - Button inputs have internal pull-up resistors Typical Applications MCS3122 is ideal for Remote Keyless Entry (RKE) applications. These applications include:
• Automotive RKE Systems
• Automotive Alarm Systems
• Gate and Garage Door Openers
• Home Security Systems
• Security and Safety Sensors
• Remote Control
• Remote Keypad
• Wireless Sensors Package Type
• 14-Pin TSSOP FIGURE 1: 14-PIN TSSOP VDD LED CTRL_OUT SW2 VDD CTRL_IN RFOUT SW0 SW1 DATA_OUT XTAL DATA_IN V SS VSS MCS3122 TABLE 1: PIN DESCRIPTION Name 14-Pin TSSOP Input Type Output Type Description VDD 1 Power — Power LED 2 — TTL LED Output (active-low) CTRL_OUT 3 — TTL Transmitter Clock SW2 4 TTL — Switch 2 Input V DD 5 Power — Power CTRL_IN 6 TTL — Transmitter Clock RFOUT 7 — RF Transmitter Output V SS 8 Power — Power DATA_IN 9 TTL — Transmitter Data XTAL 10 Analog — Transmitter Reference Oscillator DATA_OUT 11 — TTL Transmitter Data SW1 12 TTL — Switch 1 Input SW0 13 TTL — Switch 0 Input V SS 14 Power — Power MCS3122 Advanced KEELOQ® Technology Encoder Data Sheet

DS40001762A-page 2  2014 Microchip Technology Inc. Table of Contents TO OUR VALUED CUSTOMERS It is our intention to provide our valued customers with the best documentation possible to ensure successful use of your Microchip products. To this end, we will continue to improve our publications to better suit your needs. Our publications will be refined and enhanced as new volumes and updates are introduced. If you have any questions or comments regardi ng this publication, please contact the Marketing Communications Department via E-mail at docerrors@microchip.com. We welcome your feedback. Most Current Data Sheet To obtain the most up-to-date version of this data sheet, please register at our Worldwide Web site at: http://www.microchip.com You can determine the version of a data sheet by examining its literature number found on the bottom outside corner of any page . The last character of the literature number is the versio n number, (e.g., DS30000000A is version A of document DS30000000). Errata An errata sheet, describing minor operational differences from the data sheet and recommended workarounds, may exist for current devices. As device/documentation issues become known to us, we will publish an errata sheet. The errata will specify the revisi on of silicon and revision of document to which it applies. To determine if an errata sheet exists for a particular device, please check with one of the following:

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 2014 Microchip Technology Inc. DS40001762A-page 3 MCS3122

1.0 GENERAL DESCRIPTION

MCS3122 is a K EELOQ encoder, designed for secure Remote Keyless Entry (RKE) and secure remote control systems. MCS3122 utilizes the Advanced K EELOQ code hopping technology. The encoder incorporates a high- security, low-cost small package outline to make this device the perfect solution for unidirectional authentication systems and access control systems. The Advanced K EELOQ technology uses the industry standard AES-128 encryption algorithm, a serial number and a message counter which continuously increments with each button press. The crypt key, serial number and configuration data are stored in a Flash array which is not accessible via any external connection. The Flash data is programmable but read-protected. The data can be verified only after an automatic erase and programming operation. This protects against attempts to gain access to keys or manipulate synchronization values. In addition, MCS3122 provides an easy to use serial interface for programming the necessary keys, system parameters and configuration data.

1.1 Key Terms

The following is a list of key terms used throughout this data sheet. For additional information on K EELOQ technology and code hopping, refer to “An Introduction to KEELOQ® Code Hopping” Technical Brief (DS91002).

• RKE: Remote Keyless Entry
• Function Code: It indicates what button input(s) activated the transmission. It encompasses the function code bits.
• Code Hopping : A method by which a code, viewed externally to the system, appears to change unpredictably each time it is transmitted.
• Code Word : A block of data that is repeatedly transmitted upon button activation.
• Transmission: A data stream consisting of repeating code words.
• Crypt Key: A unique and secret number (128-bit for Advanced K EELOQ technology) used to encrypt and decrypt data. In a symmetrical block cipher such as those used on MCS3122, the encryption and decryption keys are equal and, therefore, will generally be referred to as the crypt key.
• Encoder: A device that generates and encodes data.
• Encryption Algorithm: A method whereby data is scrambled using a crypt key. The data can only be interpreted by the respective decryption algorithm using the same crypt key.
• Decoder: A device that decodes data received from an encoder.
• Decryption Algorithm : A recipe whereby data, scrambled by an encryption algorithm, can be unscrambled using the same crypt key.
• Learn: Learning involves the receiver calculating the transmitter’s appropriate crypt key, decrypting the received hopping code and storing the serial number, synchronization counter or timer value, and crypt key in EEPROM. The K EELOQ technology product family facilitates several learning strategies to be implemented on the decoder. The following are examples of what can be done: - Simple Learning: The receiver uses a fixed crypt key. The crypt key is common to every component used by the same manufacturer. - Normal Learning : The receiver derives a crypt key from the encoder serial number. Every transmitter has a unique crypt key. - Secure Learning : The receiver derives a crypt key from the encoder seed value. Every encoder has a unique seed value that is only transmitted by a special button combination.
• Manufacturer’s Code : A unique and secret number (128-bit for Advanced K EELOQ technology) used to derive crypt keys. Each encoder is programmed with a crypt key that is a function of the manufacturer’s code. Each decoder is programmed with the manufacturer’s code itself. The MCS3122 code hopping encoder is designed specifically for keyless entry systems. Typical applications include vehicles and home garage door openers. The encoder portion of a keyless entry system is integrated into a transmitter carried by the user. The transmitter is operated to gain access to a vehicle or a restricted area. MCS3122 is meant to be a cost- effective, yet secure solution to such systems, requiring very few external components (see Figure 2-1). Most low-end keyless entry transmitters are given a fixed identification code that is transmitted every time a button is pushed. The number of unique identification codes in a low-end system is usually a relatively small number. These shortcomings provide an opportunity for a sophisticated thief to create a device that ‘grabs’ a transmission and retransmits it later, or a device that quickly ‘scans’ all possible identification codes until the correct one is found. Advanced K EELOQ technology uses the industry standard AES-128 encryption algorithm to obscure data using 128 bits for both its block and key length. In addition to the security of Advanced K EELOQ technology, the encoder sends a message authorization block which is used to separate the message encryption from the message authentication.

DS40001762A-page 4  2014 Microchip Technology Inc.

2.0 DEVICE DESCRIPTION

As shown in the typical application circuit (Figure 2-1), MCS3122 is a simple device to use. It requires only the addition of up to three buttons, a transmitter reference oscillator, and RF circuitry for use as the transmitter in the security application. See Table 1 for a description of each pin. FIGURE 2-1: TYPICAL CIRCUIT XTAL LED VDDVDD Matching Circuit Block VDD VSS LED CTRL_OUT SW2 VDD CTRL_IN RFOUT SW0 SW1 DATA_OUT XTAL DATA_IN VSS

 2014 Microchip Technology Inc. DS40001762A-page 5 MCS3122

3.0 MEMORY ORGANIZATION

MCS3122 has 64 bytes of configuration data. In general, the Configuration bytes can be divided into two categories: those options related to the Advanced K EELOQ technology encoder and those related to the transmitter and device operation.

3.1 Counter and Protection

The synchronization counter is read, checked for integrity, updated (incremented) and saved back to Flash during normal operation of the device. The special operation prevents against data loss from unexpected power loss. An 8-bit checksum is calculated and stored alongside the synchronization counter. The checksum is calculated as a two’s complement checksum. If there is a mismatch, the second copy of the synchronization counter is read instead. Example 3-1 illustrates how to compute this value. EXAMPLE 3-1: CHECKSUM CALCULATION TABLE 3-1: CONFIG URATION REGISTERS Address Size (Bytes) Description 0x00-0x02 3 Synchronization Counter, Copy A 0x03 1 Synchronization Counter Checksum 0x04-0x07 4 Reserved (set to 0xFF) 0x08-0x0A 3 Synchronization Counter, Copy B 0x0B 1 Reserved (set to 0xFF) 0x0C-0x0F 4 Seed Transmission Serial Number (usually set to 0xFFFFFFFF) 0x10-0x1F 16 Encryption Key 0x20-0x2F 16 Authorization Key 0x30-0x33 4 Serial Number 0x34-0x35 2 Transmitter Settings 0x36-0x37 2 Reserved (set to 0xFF) 0x38-0x3F 8 Seed Value static uint8_t crc(const uint8_t* buffer, size_t len){ uint8_t bitcount; uint8_t checksum = 0xFF; while(len--) c = c + *buffer++; return 0-c;

DS40001762A-page 6  2014 Microchip Technology Inc.

3.2 Configuration Byte Details

The following tables describe Configuration bytes in detail. TABLE 3-2: ADVANCED K EELOQ® TECHNOLOGY SYNCHRONIZATION REGISTERS, COPY A Byte Address Bit Description Values 0x00 7:0 Synchronization Counter, Copy A Byte 0 of the synchronization counter (LSB) 0x01 7:0 Byte 1 of the synchronization counter 0x02 7:0 Byte 2 of the synchronization counter (MSB) 0x03 7:0 Checksum Checksum of the synchronization counter TABLE 3-3: ADVANCED K EELOQ® TECHNOLOGY SYNCHRONIZATION REGISTERS, COPY B Byte Address Bit Description Values 0x08 7:0 Synchronization Counter, Copy B Byte 0 of the synchronization counter (LSB) 0x09 7:0 Byte 1 of the synchronization counter 0x0A 7:0 Byte 2 of the synchronization counter (MSB) TABLE 3-4: ADVANCED K EELOQ® TECHNOLOGY SEED SERIAL NUMBER REGISTERS Byte Address Bit Description Values 0x0C 7:0 Seed Serial Number Byte 0 of the seed serial number (LSB) 0x0D 7:0 Byte 1 of the seed serial number 0x0E 7:0 Byte 2 of the seed serial number 0x0F 7:0 Byte 3 of the seed serial number (MSB) TABLE 3-5: ADVANCED K EELOQ® TECHNOLOGY CRYPT KEY REGISTERS Byte Address Bit Description Values 0x10 7:0 Crypt Key Byte 0 of the crypt key (LSB) 0x11 7:0 Byte 1 of the crypt key 0x12 7:0 Byte 2 of the crypt key 0x13 7:0 Byte 3 of the crypt key 0x14 7:0 Byte 4 of the crypt key 0x15 7:0 Byte 5 of the crypt key 0x16 7:0 Byte 6 of the crypt key 0x17 7:0 Byte 7 of the crypt key 0x18 7:0 Byte 8 of the crypt key 0x19 7:0 Byte 9 of the crypt key 0x1A 7:0 Byte 10 of the crypt key 0x1B 7:0 Byte 11 of the crypt key 0x1C 7:0 Byte 12 of the crypt key 0x1D 7:0 Byte 13 of the crypt key 0x1E 7:0 Byte 14 of the crypt key 0x1F 7:0 Byte 15 of the crypt key (MSB)

 2014 Microchip Technology Inc. DS40001762A-page 7 MCS3122 TABLE 3-6: ADVANCED K EELOQ® TECHNOLOGY AUTHORIZATION KEY REGISTERS Byte Address Bit Description Values 0x20 7:0 Authorization Key Byte 0 of the authorization key (LSB) 0x21 7:0 Byte 1 of the authorization key 0x22 7:0 Byte 2 of the authorization key 0x23 7:0 Byte 3 of the authorization key 0x24 7:0 Byte 4 of the authorization key 0x25 7:0 Byte 5 of the authorization key 0x26 7:0 Byte 6 of the authorization key 0x27 7:0 Byte 7 of the authorization key 0x28 7:0 Byte 8 of the authorization key 0x29 7:0 Byte 9 of the authorization key 0x2A 7:0 Byte 10 of the authorization key 0x2B 7:0 Byte 11 of the authorization key 0x2C 7:0 Byte 12 of the authorization key 0x2D 7:0 Byte 13 of the authorization key 0x2E 7:0 Byte 14 of the authorization key 0x2F 7:0 Byte 15 of the authorization key (MSB) TABLE 3-7: ADVANCED K EELOQ® TECHNOLOGY SERIAL NUMBER REGISTERS Byte Address Bit Description Values 0x30 7:0 Serial Number Byte 0 of the serial number (LSB) 0x31 7:0 Byte 1 of the serial number 0x32 7:0 Byte 2 of the serial number 0x33 7:0 Byte 3 of the serial number (MSB)

DS40001762A-page 8  2014 Microchip Technology Inc. TABLE 3-8: TRANSMITTER CONFIGURATION REGISTERS Byte Address Bit Description Values 0x34 7:6 FSK Frequency Deviation 11 – 200 kHz 10 – 100 kHz 01 – 75 kHz 10 – 50 kHz 5O u t p u t P o w e r 0 – 0 dBm 1 – 10 dBm

4 Encoding 1 – PWM

0 – Manchester

3 Modulation 1 – OOK

0 – FSK 2:0 Frequency Select 000 – 315.00 MHz (only with 24 MHz crystal) 001 – 390.00 MHz 010 – 418.00 MHz 011 – 433.92 MHz 100 – 868.30 MHz 101 – 868.65 MHz 110 – 868.95 MHz 111 – 915.00 MHz 0x35 3 and 1:0 Seed Button Configuration 111 – Disabled, no seed option 110 – SW0 101 – SW1 100 – SW1 and SW0 011 – SW2 010 – SW2 and SW0 001 – SW2 and SW1 000 – SW3, SW2 and SW1

2 Authorization Code Enable 1 – Enabled

0 – Disabled 5:4 Baud Rate 11 – 200 µS 10 – 150 µS 11 – 100 µS 11 – 50 µS 7:6 Maximum Code Words 11 – 234 words 10 – 80 words 01 – 4 words 00 – No maximum limit TABLE 3-9: ADVANCED K EELOQ® TECHNOLOGY SEED CONFIGURATION REGISTERS Byte Address Bit Description Values 0x38 7:0 Seed Value Byte 0 of the seed value (LSB) 0x39 7:0 Byte 1 of the seed value 0x3A 7:0 Byte 2 of the seed value 0x3B 7:0 Byte 3 of the seed value 0x3C 7:0 Byte 4 of the seed value 0x3D 7:0 Byte 5 of the seed value 0x3E 7:0 Byte 6 of the seed value 0x3F 7:0 Byte 7 of the seed value (MSB)

 2014 Microchip Technology Inc. DS40001762A-page 9 MCS3122

4.0 ADVANCED K EELOQ®

4.1 Synchronization Counter

This is the 24-bit synchronization value that is used to create the hopping code for transmission. This value will be incremented after every transmission. The initial value of the synchronization counter may be set via the Synchronization Counter Initial Value registers (see Table 3-2 and Table 3-3).

4.2 Function Code (Button Status

Code) The function code is a bitmapped representation of the state of each button on the transmitter. States are active-high.

4.3 Serial Number

Each Advanced K EELOQ encoder transmits its 32-bit serial number with each transmission. It is intended that this serial number be unique to a system. It is set in the Serial Number Configuration registers, listed in Table 3-7.

4.4 Seed Code Serial Number

The transmitter has the possibility to set the serial number which will be transmitted with a seed transmission. In a typical system, this serial number is transmitted as 0xFFFFFFFF; however, the user can configure this according to the actual application. The seed code serial number is set in the Seed Code Configuration registers, listed in Table 3-4. TABLE 4-1: ADVANCED K EELOQ® BUTTON CODE TRANSLATION Button Function Code SW0 xx1 SW1 x1x SW2 1xx

DS40001762A-page 10  2014 Microchip Technology Inc.

4.5 Code Word Format

The Advanced K EELOQ code word is either 160 or 192-bit long. It comprises three sections (see Figure 4-1):

• 32 Bits of the Encoder’s Serial Number
• 128 Bits of the Encrypted Hopping Code
• 32 Bits of the Authorization Code (optional) These segments are described in detail in the following sections. FIGURE 4-1: ADVANCED K EELOQ® CODE WORD FORMAT

4.5.1 FIXED CODE PORTION

The fixed code portion consists of 32 bits of the serial number.

4.5.2 HOPPING CODE PORTION

The hopping code portion is calculated by encrypting the synchronization counter and function code with the encoder key. The hopping code is calculated when a button press is registered.

4.5.3 AUTHORIZATION CODE PORTION

The authorization code is a cryptographically-strong industry standard representation of the code word suitable for authentication and integrity verification. It is generated by using the on-board AES encryption algorithm in CBC-MAC mode. The calculation takes place over the entire code word, including the encrypted and unencrypted portions, using the authorization key as input. Figure 4-2 shows a representation of how this calculation is performed. This calculation is truncated to its Least Significant 32 bits for transmission. The authorization code requires a shared secret called the authorization key. This key is set in the Authorization Key Configuration register, listed in Table 3-6. FIGURE 4-2: AUTHORIZATION CODE CALCULATION The authorization code portion consists of the 32-bit Least Significant bits of the authorization code. Serial Number 0x55AA55 32 bits Fixed Portion 128 bits Encrypted Hopping Code Authorization Code 32 bits Auth Portion Sync. Counter 0x55 Function Code 0xAA55AA55 0xAA55 0xAA55 32-bits 24-bits 24-bits 8-bits 8-bits 32-bits 16-bits 16-bits 32-bits Note: The data is sent LSB first (in this figure from right to left). Serial Encrypted Authorization Key Authorization CodeE E Number Code Word

 2014 Microchip Technology Inc. DS40001762A-page 11 MCS3122

4.5.4 SEED WORD FORMAT

The seed word is used when pairing the transmitter to a receiver using a secure learn methodology. The seed code word format is shown is Figure 4-3. While the MCS3122 Flash data contains user-configurable 64-bit seed data, the encoder will send 128-bit seed code. The 128-bit seed code is constructed using the user-configured seed code for the lower 64 bits of the seed. The upper 64 bits are added by MCS3122 as 8 bytes with a 0x12 value. FIGURE 4-3: ADVANCED K EELOQ® SEED WORD FORMAT(1) Serial Number 64-Bit Padded Seed Upper Value(2) 64-Bit Configurable Seed Lower Value 32 bits Fixed Portion 128 bit Seed Authorization Code 32 bits Auth. Portion Note 1: MCS3122 can set a different serial number for the seed packet. This is typically set to 0xFFFFFFFF. 2: The padded value is 0x1212121212121212. 3: The data is sent LSB first (in this figure from right to left.

DS40001762A-page 12  2014 Microchip Technology Inc.

5.0 TRANSMITTER OPERATION

5.1 Data Modulation Format and Baud

A transmission is made up of several code words. Each code word contains a preamble, header and data. A code word is separated from another code word by guard time. All timing specifications for the modulation formats are based on a basic Time Element, described as T E. See Section 5.2 “Baud Rate” for details on baud rate calculation. This timing element can be set to a wide range of values. The length of the preamble, header and guard is fixed. The guard time is fixed to a typical 18.5 ms. FIGURE 5-1: PWM TRANSMISSION FORMAT FIGURE 5-2: MANCHESTER TRANSMISSION FORMAT 11 6

31 TE Preamble 10 TE

Header Encrypted Portion Fixed Code Portion Guard Time TE TE TE TBP Logic ‘0’ Logic ‘1’ 11 6 Preamble Encrypted Portion Fixed Code Portion Guard Time TE TE TBP Logic ‘0’ Logic ‘1’ 10 TE Header bit 1bit 0 bit 2Start bit Stop bit

 2014 Microchip Technology Inc. DS40001762A-page 13 MCS3122

5.2 Baud Rate

The baud rate of an encoder’s transmission is highly configurable using the two bits in the Transmitter Setting Byte 1 register (0x35).

5.3 Transmission Modulation Format

The RF transmission can be configured to modulate using Frequency-Shift Keying (FSK) or On-Off Keying (OOK). The selection is done using one bit in the Transmitter Settings Byte 0 register (0x34).

5.4 Frequency and Band Selection

The RF frequency configuration is performed by selecting the appropriate bits in the Transmitter Settings Byte 0 register (0x34).

5.5 Deviation Selection

When using FSK modulation, the frequency deviation can be configured using bits <7:6> in the Transmitter Settings Byte 0 register (0x34).

5.6 Power Output

The RF output power can be configured to either 0 dBm or 10 dBm. The setting is done using bit <5> in the Transmitter Settings Byte 0 register (0x34). TABLE 5-1: BAUD RATE SELECTION OPTIONS TE (µS) Bits <5:4> 200 1:1 150 1:4 100 1:4 50 1:16 TABLE 5-2: MODUL ATION FORMAT SELECTION OPTIONS Modulation Bit <3> FSK 0 OOK 1 TABLE 5-3: FREQUENCY SELECTION OPTIONS Frequency Bits <2:0>

315.00 MHz(1) 000

390.00 MHz 001

418.00 MHz 010

433.92 MHz 011

868.30 MHz 100

868.65 MHz 101

868.90 MHz 110

915.00 MHz 111

Note 1: For 315.00 MHz operation, a 24 MHz crystal is required. All the other frequency settings will require a 26 MHz crystal. TABLE 5-4: FREQUENCY DEVIATION SELECTION OPTIONS Deviation Bits <7:6> 200 kHz 11 100 kHz 10 75 kHz 01 50 kHz 00 TABLE 5-5: OUTPUT POWER SELECTION OPTIONS Out Power Bit <5> 0 dBm 0 10 dBm 1

DS40001762A-page 14  2014 Microchip Technology Inc.

5.7 Crystal Selection

Once the frequency band has been selected, the choice of crystal frequency is flexible provided the crystal meets the specifications summarized in Table 5-6, the boundaries of the Encoder Frequency Configuration value are followed and the RF transmit frequency error is acceptable to the system design.

5.8 Seed Button Configuration

The MCS3122 allows the user to select which button combination will output the seed transmission instead of the normal data packet. Table 5-7 lists all the possible button combinations.

5.9 Code Word Completion

MCS3122 always ensures that a full and complete code word is transmitted even if all buttons are released before transmission is complete.

5.10 Maximum Code Words

This feature sets a maximum number of code words transmitted by a button configuration. If a button is kept pressed, the maximum allowed code words will be transmitted. If a new button is pressed or a new button press combination is used, the process will be restarted and the maximum number of words will be transmitted. TABLE 5-6: CRYSTAL RESO NATOR SPECIFICATIONS Symbol Description Min. Typ. Max. Unit fREF Crystal Frequency — 26 or 24 (1) —M H z CL Load Capacitance — 15 — pF ESR Equivalent Series Resistance — — 100 Ω Note 1: When selecting the 315.000 MHz frequency, a 24 MHz crystal is required. TABLE 5-7: SEED BUTTON CONFIGURATION OPTIONS SW2 SW1 SW0 Bit Settings <3> and <1:0> Closed Closed Closed 000 Closed Closed Open 001 Closed Open Closed 010 Closed Open Open 011 Open Closed Closed 100 Open Closed Open 101 Open Open Closed 110 Open Open Open 111(1) Note 1: The button combination corresponding to the setting ‘111’ will not generate a seed combination since it corresponds to all buttons not pressed. Setting the bits to this value will disable the seed packet sending (i.e., no button combination will send a seed code).

 2014 Microchip Technology Inc. DS40001762A-page 15 MCS3122

6.0 INTEGRATING MCS3122 INTO

FIGURE 6-1: TYPICAL DECODER OPERATION

6.1 Decoder Operation

The decoder waits until a transmission is received. The received serial number is compared to the EEPROM table of learned transmitters to first determine if this transmitter’s use is allowed in the system. If from a paired transmitter, the transmission is decrypted using the stored crypt key and authenticated via the Discrimination bits for appropriate crypt key usage. If the decryption is valid, the synchronization value is evaluated (see Figure 6-1).

6.2 Synchronization with a Decoder

The K EELOQ technology includes a sophisticated synchronization technique that does not require the calculation and storage of future codes. The technique securely blocks invalid transmission while providing transparent resynchronization to transmitters inadvertently activated away from the receiver. Figure 6-2 shows a three-partition, rotating Synchronization window. The size of each window is optional but the technique is fundamental. Each time a transmission is authenticated, the intended function is executed and the transmission’s synchronization counter value is stored in EEPROM. From the currently stored counter value there is an initial Single Operation Forward window of 16 codes. If the difference between a received synchronization counter and the last stored counter is within 16, the intended function will be executed on a single button press and the new synchronization counter will be stored. Storing the new synchronization counter value effectively rotates the entire Synchronization window. A Double Operation (Resynchronization) window further exists from the Single Operation window up to 8M code forward of the currently stored counter value. It is referred to as Double Operation because a transmission with a synchronization counter in this window will require an additional, sequential counter transmission prior to executing the intended function. Upon receiving the sequential transmission the decoder executes the intended function and stores the synchronization counter value. This resynchronization occurs transparently to the user, as it is human nature to press the button a second time if the first was unsuccessful. The third window is a Blocked window ranging from the Double Operation window to the currently stored synchronization counter value. Any transmission with synchronization counter value within this window will be ignored. This window excludes previously used code-grabbed transmissions from accessing the system. Rev. 20-000013A 1/29/2014 Start Does Serial Number Match? Transmission Received? Is Counter Within 16? Is Counter Within 32K? Decrypt Transmission Is Decryption Valid? Save Counter in Temporary Location Execute Command and Update Counter Yes Yes Yes Yes Yes No No No No No Note: The synchronization method described in this section is an exemplar method. It may be altered to fit the needs and capabilities of a particular system.

DS40001762A-page 16  2014 Microchip Technology Inc. FIGURE 6-2: SYNCHRONIZATION WINDOW

6.3 Security Considerations

The strength of this security is based on keeping a secret inside the transmitter that can be verified by encrypted transmissions to a trained receiver. The transmitter’s secret is the manufacturer’s key, not the encryption algorithm. If that key is compromised, then a smart transceiver can capture any serial number, create a valid code word and trick all receivers trained with that serial number. The key cannot be read from the EEPROM without costly die probing, but it can be calculated by brute force decryption attacks on transmitted code words. The cost for these attacks should exceed what the manufacturer would want to protect. To protect the security of other receivers with the same manufacturer’s code, the manufacturer should use the random seed for secure learn. It is a second secret that is unique for each transmitter. If a manufacturer’s key is compromised, clone transmitters can be created, but without the unique seed, they have to be relearned by the receiver. In the same way, if the transmissions are decrypted by brute force on a computer, the random seed hides the manufacturer’s key and prevents more than one transmitter from being compromised. The length of the code word at these baud rates make brute force attacks that guess the hopping code take years. To make the receiver less susceptible to this attack, it should test all bits in the decrypted code for the correct value, not just the low counter bits and function code. The main benefit of hopping codes is to prevent the retransmission of captured code words. This works very well for code words which the receiver decodes. Its weakness is that, if a code is captured when the receiver misses it, the code may trick the receiver once if it is used before the next valid transmission. The receiver should increment the counter on questionable code word receptions. The transmitter should use separate buttons for lock and unlock functions. A different method would be to require two different buttons in sequence to gain access. There are more ways to make K EELOQ systems more secure, but they all have trade-offs. The user should find a balance between security, design effort and usability, particularly in failure modes. For example, if a button sticks or kids play with it, the counter should not advance into the Blocked Code window, rendering the transmitter useless or requiring retraining. Blocked Window (8M Codes) Double Operation (Resynchronization Window) (8M Codes) Stored Synchronization Counter Value Single Operation Window (16 Codes) Entire window rotates to eliminate use of previously used codes

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7.0 ELECTRICAL SPECIFICATIONS

7.1 Absolute Maximum Ratings (†)

Voltage on pins with respect to VSS Maximum current

7.2 Standard Operating Conditions

The standard operating conditions for any device are defined as: Operating Voltage: V DDMIN VDD VDDMAX Operating Temperature: T A_MIN TA TA_MAX VDD — Operating Supply Voltage TA — Operating Ambient Temperature Range IDD — Supply Current IPD — Standby Current VOH — Output High Voltage VOL — Output Low Voltage † NOTICE: Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operation listings of this specification is not implied. Exposure above maximum rating conditions for extended periods may affect device reliability. Note 1: Typical values are at 25°C.

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8.0 PACKAGING INFORMATION

8.1 Package Marking Information

• Standard PIC® device marking consists of Microchip part number, year code, week code, and traceability code. For PIC device marking beyond this, certain price adders apply. Please check with your Microchip Sales Office. For QTP devices, any special marking adders are included in QTP price. 14-Lead TSSOP (4.4 mm) Example YYWW NNN XXXXXXXX MCS3122 1409 017 Legend: XX...X Customer-specific information Y Year code (last digit of calendar year) YY Year code (last 2 digits of calendar year) WW Week code (week of January 1 is week ‘01’) NNN Alphanumeric traceability code Pb-free JEDEC ® designator for Matte Tin (Sn) * This package is Pb-free. The Pb-free JEDEC designator ( ) can be found on the outer packaging for this package. Note: In the event the full Microchip part number cannot be marked on one line, it will be carried over to the next line, thus limiting the number of available characters for customer-specific information.

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8.2 Package Details

The following sections give the technical details of the packages. Note: For the most current package drawings, please see the Microchip Packaging Specification located at http://www.microchip.com/packaging

DS40001762A-page 20  2014 Microchip Technology Inc. Note: For the most current package drawings, please see the Microchip Packaging Specification located at http://www.microchip.com/packaging

 2014 Microchip Technology Inc. DS40001762A-page 21 MCS3122 Note: For the most current package drawings, please see the Microchip Packaging Specification located at http://www.microchip.com/packaging

DS40001762A-page 22  2014 Microchip Technology Inc. APPENDIX A: REVISION HISTORY Revision A (October 2014) Initial release of this document.

 2014 Microchip Technology Inc. DS40001762A-page 23 MCS3122 THE MICROCHIP WEB SITE Microchip provides online support via our WWW site at www.microchip.com. This web site is used as a means to make files and information easily available to customers. Accessible by using your favorite Internet browser, the web site contains the following information:

• Product Support – Data sheets and errata, application notes and sample programs, design resources, user’s guides and hardware support documents, latest software releases and archived software
• General Technical Support – Frequently Asked Questions (FAQ), technical support requests, online discussion groups, Microchip consultant program member listing
• Business of Microchip – Product selector and ordering guides, latest Microchip press releases, listing of seminars and events, listings of Microchip sales offices, distributors and factory representatives CUSTOMER CHANGE NOTIFICATION SERVICE Microchip’s customer notification service helps keep customers current on Microchip products. Subscribers will receive e-mail notification whenever there are changes, updates, revisions or errata related to a specified product family or development tool of interest. To register, access the Microchip web site at www.microchip.com. Under “Support”, click on “Customer Change Notification” and follow the registration instructions. CUSTOMER SUPPORT Users of Microchip products can receive assistance through several channels:
• Distributor or Representative
• Local Sales Office
• Field Application Engineer (FAE)
• Technical Support Customers should contact their distributor, representative or Field Application Engineer (FAE) for support. Local sales offices are also available to help customers. A listing of sales offices and locations is included in the back of this document. Technical support is available through the web site at: http://microchip.com/support.

DS40001762A-page 24  2014 Microchip Technology Inc. PRODUCT IDENTIFICATION SYSTEM To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office . PART NO. X /XX XXX PatternPackageTemperature Range Device Device: MCS3122 Tape and Reel Option: Blank = Standard packaging (tube or tray) T = Tape and Reel (1) Temperature Range: I= - 4 0 C to +85 C (Industrial) Package:(2) ST = TSSOP Pattern: QTP , SQTP , Code or Special Requirements (blank otherwise) Examples: a) MCS3122 - I/ST Industrial temperature, TSSOP package Note 1: Tape and Reel identifier only appears in the catalog part number description. This identifier is used for ordering purposes and is not printed on the device package. Check with your Microchip Sales Office for package availability with the Tape and Reel option. 2: For other small form-factor package availability and marking information, please visit www.microchip.com/packaging or contact your local sales office. X Tape and Reel Option

 2014 Microchip Technology Inc. DS40001762A-page 25 Information contained in this publication regarding device applications and the like is provided only for your convenience and may be superseded by updates. It is your responsibility to ensure that your application meets with your specifications. MICROCHIP MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL, STATUTORY OR OTHERWISE, RELATED TO THE INFORMATION, INCLUDING BUT NOT LIMITED TO ITS CONDITION, QUALITY , PERFORMANCE, MERCHANTABILITY OR FITNESS FOR PURPOSE . Microchip disclaims all liability arising from this information and its use. Use of Microchip devices in life support and/or safety applications is entirely at the buyer’s risk, and the buyer agrees to defend, indemnify and hold harmless Microchip from any and all damages, claims, suits, or expenses resulting from such use. No licenses are conveyed, implicitly or otherwise, under any Microchip intellectual property rights. Trademarks The Microchip name and logo, the Microchip logo, dsPIC, FlashFlex, flexPWR, JukeBlox, KEELOQ, KEELOQ logo, Kleer, LANCheck, MediaLB, MOST, MOST logo, MPLAB, OptoLyzer, PIC, PICSTART, PIC 32 logo, RightTouch, SpyNIC, SST, SST Logo, SuperFlash and UNI/O are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. The Embedded Control Solutions Company and mTouch are registered trademarks of Microchip Technology Incorporated in the U.S.A. Analog-for-the-Digital Age, BodyCom, chipKIT, chipKIT logo, CodeGuard, dsPICDEM, dsPICDEM.net, ECAN, In-Circuit Serial Programming, ICSP, Inter-Chip Connectivity, KleerNet, KleerNet logo, MiWi, MPASM, MPF, MPLAB Certified logo, MPLIB, MPLINK, MultiTRAK, NetDetach, Omniscient Code Generation, PICDEM, PICDEM.net, PICkit, PICtail, RightTouch logo, REAL ICE, SQI, Serial Quad I/O, Total Endurance, TSHARC, USBCheck, VariSense, ViewSpan, WiperLock, Wireless DNA, and ZENA are trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. SQTP is a service mark of Microchip Technology Incorporated in the U.S.A. Silicon Storage Technology is a registered trademark of Microchip Technology Inc. in other countries. GestIC is a registered trademarks of Microchip Technology Germany II GmbH & Co. KG, a subsidiary of Microchip Technology Inc., in other countries. All other trademarks mentioned herein are property of their respective companies. © 2014, Microchip Technology Incorporated, Printed in the U.S.A., All Rights Reserved. ISBN: 978-1-63276-724-0 Note the following details of the code protection feature on Microchip devices:

• Microchip products meet the specification cont ained in their particular Microchip Data Sheet.
• Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used i n the intended manner and under normal conditions.
• There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
• Microchip is willing to work with the customer who is concerned about the integrity of their code.
• Neither Microchip nor any other semiconduc tor manufacturer can guarantee the security of their code. Code protection does not mean that we are guaranteeing the product as “unbreakable.” Code protection is constantly evolving. We at Microchip are co mmitted to continuously improvin g the code protection features of our products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act. Microchip received ISO/TS-16949:2009 certification for its worldwide headquarters, design and wafer fabrication facilities in Chandler and Tempe, Arizona; Gresham, Oregon and design centers in California and India. The Company’s quality system processes and procedures are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping devices, Serial EEPROMs, microperipherals, nonvolatile memory and analog products. In addition, Microchip’s quality system for the design and manufacture of development systems is ISO 9001:2000 certified. QUALITY MANAGEMENT S YSTEM CERTIFIED BY DNV == ISO/TS 16949 ==

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