MT8843

MT8843 MITEL | Alldatasheet

Document overview

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Technical content

Features

• Compatible with British Telecom (BT) SIN227 & SIN242, Cable T elevision Association (CTA) TW/P&E/312, and Bellcore TR-NWT-000030 & SR-TSV-002476
• Ring and line reversal detection
• Bellcore "CPE Alerting Signal (CAS)" and BT "Idle State Tone Alert Signal" detection
• 1200 baud BELL 202 and CCITT V.23 Frequency Shift Keying (FSK) demodulation
• High input sensitivity
• Dual mode 3-wire data interface
• Low power CMOS with powerdown mode
• Input gain adjustable amplifier
• Carrier detect status output
• Uses 3.58 MHz crystal or ceramic resonator

Applications

• BT Calling Line Identity Presentation (CLIP), CTA CLIP , and Bellcore Calling Identity Delivery (CID) systems
• Feature phones, including Analog Display Services Interface (ADSI) phones
• Phone set adjunct boxes
• FAX and answering machines
• Database query and Computer Telephony Integration (CTI) systems

Description

The MT8843 Calling Number Identification Circuit 2 (CNIC2) is a low power CMOS integrated circuit intended for receiving physical layer signals transmitted according to BT (British Telecom) SIN227 & SIN242, CTA (Cable TV Association) TW/ P&E/312 and Bellcore TR-NWT-000030 & SR-TSV- 002476 specifications. The CNIC2 provides all the features and functions offered by Mitel’s MT8841 (CNIC), including 1200 baud BELL 202 and CCITT V.23 FSK demodulation. The 3-wire serial FSK interface provided by CNIC has been enhanced to operate in two modes. The first mode is the CNIC compatible mode whereby data transfer is initiated by the device. The new, second mode allows a microcontroller to extract 8-bit data words from the device. Furthermore, CNIC2 offers Idle State T one Alert Signal and line reversal detection capability for BT’s CLIP , ring burst detection for CTA’s CLIP , and ring detection for Bellcore’s CID. Figure 1 - Functional Block Diagram Anti-alias Filter FSK Bandpass Filter FSK Demodulator Data Timing Recovery Carrier Detector Alert Signal High Tone Filter Alert Signal Low Tone Filter Tone Detection Algorithm Bias Generator Oscillator Guard Time StD St/GT ESt TRIGoutTRIGRCTRIGin DATA DR DCLK MODEFSKen CD CAP OSCin OSCout IN+ IN- GS VRef INT PWDN VDD VSS To internal To internal cct. cct. Interrupt Generator ISSUE 1 February 1995

Ordering Information

MT8843AE 24 Pin Plastic DIP MT8843AS 24 Pin SOIC -40 °C to +85 °C MT8843 Calling Number Identification Circuit 2 CMOS Preliminary Information

Preliminary Information MT8843 5-23 18 DR 3-wire FSK Interface Data Ready (CMOS Output). Active low.This output goes low after the last DCLK pulse of each word. This identifies the data (8-bit word) boundary on the serial output stream. Typically, DR is used to latch 8-bit words from the serial-to-parallel converter into a microcontroller. 19 CD Carrier Detect (CMOS Output). Active low. A logic low indicates the presence of in-band signal at the output of the FSK bandpass filter. 20 INT Interrupt (Open Drain Output). Active low. It is active when TRIGout or DR is low, or StD is high. This output stays low until all three signals have become inactive. 21 StD Dual Tone Alert Signal Delayed Steering Output. When high, it indicates that a guard time qualified alert signal has been detected. 22 ESt Dual Tone Alert Signal Early Steering Output. Alert signal detection output. Used in conjunction with St/GT and external circuitry to implement detect and non-detect guard times. 23 St/GT Dual Tone Alert Signal Steering Input/Guard Time (Analog Input/CMOS Output). A voltage greater than VTGt detected at St causes the device to register the detected tone pair and update the output latch. A voltage less than VTGt frees the device to accept a new tone pair. The GT output acts to reset the external steering time-constant; its state is a function of ESt and the voltage on St. 24 V DD Positive Power Supply. Pin Description Pin # Name Description Functional Overview The MT8843 Calling Number Identification Circuit 2 (CNIC2) is a device compatible with BT, CTA and Bellcore specifications. As shown in Figure 1, CNIC2 provides an FSK demodulator as well as a 3-wire serial interface similar to that of it’s predecessor, the MT8841 (CNIC). The 3-wire interface has been enhanced to provide two modes of operation - a mode whereby data transfer is initiated by the device and a mode whereby data transfer is initiated by an external microcontroller. In addition to supporting all the features and functions offered by MT8841, CNIC2 provides line reversal detection, ring detection and dual tone alert signal detection capability. These new functions eliminate some external application circuitry previously required with the MT8841 (CNIC). SIN227 and SIN242 specify the signalling mechanism between a network and a T erminal Equipment (TE) providing Caller Display Service (CDS). CDS provides Calling Line Identity Presentation (CLIP), that is, delivery of the identity of the caller when a telephone call arrives, before the start of ringing (in the Idle State). An incoming CDS call is indicated by a polarity reversal on the A and B wires (line reversal), followed by an Idle State T one Alert Signal. CNIC2 has the capability to detect both the reversal and alert signal as well as to receive and demodulate the incoming CCITT V.23 FSK signals. TW/P&E/312 proposes an alternate CDS TE interface available for use in the CTA network. According to TW/P&E/312, data is transmitted after a single burst of ringing rather than before the first ringing cycle (as specified in SIN227). The Idle State T one Alert Signal is not required as it is replaced with a single ring burst. CNIC2 has the capability to detect the ring burst. It is also able to demodulate either Bell-202 or CCITT V.23 FSK data following the ring burst, as specified by the CTA. TR-NWT-000030 specifies generic requirements for transmitting asynchronous voiceband data to Customer Premises Equipment (CPE). SR-TSV- 002476 describes the same requirements from the CPE’s perspective. The data transmission technique specified in both documents is applicable in a variety of services like Calling Number Delivery (CND), Calling Name Delivery (CNAM) and Calling Identity Delivery on Call Waiting (CIDCW) - services promoted by Bellcore. In CND/CNAM service, information about a calling party is embedded in the silent interval between the first and second ring. CNIC2 detects the first ring and can then be setup to receive and demodulate the incoming Bell-202 FSK data. The device will output the demodulated data onto a 3-wire serial interface.

into sleep mode to conserve power. specified in the BT CIDCW specification in the future. at the CPE A/B (tip/ring) interface. Blue Book, volume V "T elephone Transmission Quality" 1989. than 20ms if both tones are detected. Table 1. Dual Tone Alert Signal Characteristics determine the presence of a dual tone alert signal. The ESt pin goes high when both tones are present.

• Dual Tone Detection Guard Time When the dual tone alert signal is detected by the CNIC2, ESt is pulled high. When the alerting signal ceases to be detected, ESt goes low. Figure 4 shows the relationship between the St/GT , ESt and StD pins. It also shows the operation of a guard time circuit. The guard time circuit improves detection performance by rejecting detections of insufficient duration and by allowing momentary ESt dropouts once the duration criterion has been met. The total recognition time is t REC = tGP + tDP, where tGP is the tone present guard time and tDP is the tone present detect time (refer to timing between ESt, St/ GT and StD in Figures 15 and 18). The total tone absent time is t ABS = tGA + tDA , where tGA is the tone absent guard time and tDA is the tone absent detect time (refer to timing between ESt, St/ GT and StD in Figures 15 and 18). Bellcore states that it is desirable for an off-hook capable CPE to have a CAS detector on/off switch. The switch was conceived so that a subscriber who disconnects a service that relies on CAS detection (e.g., CIDCW), but retains the CPE, can turn off the detector and not be bothered by false detection. SW1 in Figure 4 performs the above function. In the B position, the comparator input, hence StD, is always low. The CAS detector will not be enabled and its output will not cause interrupts (except for the system power up condition described in section “Interrupt” on page 28’). BT states that the idle state tone alert signal recognition time should be no less than 20ms when

with no external intervention. at the CPE tip/ring (A/B) interface. c. The frequency range is specified in TR-NWT-000030. Table 2. FSK Characteristics

• 3-wire User Interface The MT8843 provides a powerful dual mode 3-wire interface so that the 8-bit data words in the demodulated FSK bit stream can be extracted without the need either for an external UART (Universal Asynchronous Receiver Transmitter) or for the TE/CPE’s microcontroller to perform the UART function in software (asynchronous serial data reception). The interface is specifically designed for the 1200 baud rate and is comprised of the DATA, DCLK (data clock) and DR (data ready) pins. Two modes (modes 0 and 1) are selectable via control of the device’s MODE pin: in mode 0, data transfer is initiated by the CNIC2; in mode 1, data transfer is initiated by the external microcontroller. Mode 0 This mode is selected when the MODE pin is low. It is the CNIC (MT8841) compatible mode where data transfer is initiated by the device. In this mode, CNIC2 receives the FSK signal, demodulates it, and outputs the extracted data to the DATA pin (refer to Figure 12). For each received stop and start bit sequence, the CNIC2 outputs a fixed frequency clock string of 8 pulses at the DCLK pin. Each clock rising edge occurs in the centre of each DATA bit cell. DCLK is not generated for the stop and start bits. Consequently, DCLK will clock only valid data into a peripheral device such as a serial to parallel shift register or a micro-controller. CNIC2 also outputs an end of word pulse (data ready) at the DR pin. The data ready signal indicates the reception of every 10-bit word sent from the network to the TE/ CPE. This DR signal is typically used to interrupt a micro-controller. Mode 1 This mode is selected when the MODE pin is high. In this mode, the microcontroller supplies read pulses (DCLK) to shift the 8-bit data words out of the MT8843, onto the DATA pin. CNIC2 asserts DR to denote the word boundary and indicate to the microprocessor that a new word has become available (refer to Figure 14). Internally, the MT8843’s demodulated data bits are sampled and stored. After the 8th bit, the word is parallel loaded into an 8 bit shift register and DR goes low. The shift register’s contents are shifted out to the DATA pin on DCLK’s rising edge in the order they were received. If DCLK begins while DR is low, DR will return to high upon the first DCLK. This feature allows the associated interrupt (see section on "Interrupt") to be

Preliminary Information MT8843 5-29 The crystal specification is as follows: Frequency: 3.579545 MHz Frequency tolerance: ±0.1%(-40°C+85°C) Resonance mode :P a r a l l e l Load capacitance: 18 pF Maximum series resistance: 150 ohms Maximum drive level (mW):2 mW e.g., CTS MP036S Any number of MT8843 devices can be connected as shown in Figure 8 such that only one crystal is required. The connection between OSC2 and OSC1 can be D.C. coupled as shown, or the OSC1 inputs on all devices can be driven from a CMOS buffer (dc coupled) with the OSC2 outputs left unconnected. VRef and CAP Inputs V Ref is the output of a low impedance voltage source equal to VDD/2 and is used to bias the input op-amp. A 0.1µF capacitor is required between CAP and VSS to suppress noise on VRef. The circuit shown in Figure 9 illustrates the use of the MT8843 (CNIC2) device in a typical CID or CLIP sys- tem. Network protection will differ depending on the market for which the product is designed. Notes: CNIC2 has not been fully characterized for talkoff and talkdown performance as specified in SR-TSV- 002476. For CIDCW, speech immunity improves if near end audio is cancelled from the incoming signal. One possible implementation is to connect the signal input to the 2 wire side when the CPE is on-hook and the 4 wire side when the CPE is off-hook. Figure 9 - Application Circuit IN+ IN- GS VRef TRIGin TRIGRC TRIGout MODE OSCin OSCout VSS VDD St/GT ESt StD INT DR DATA DCLK FSKen PWDN IC CNIC2 CAP CD (FSK Interface Mode 0 selected) +5V = To microcontroller = From microcontroller 0.1µF TIP / A RING / B Notes MT8843 +5V +5V +5V 430K 430K 34K 34K 53K6 60K4 464K 500K 500K 200K 300K 500K 0.1µF 0.1µF 0.01µF 0.01µF 0.1µF 0.33µF 420K 420K 0.1µF TISP4180, TPA150A12 or TPB150B12 TISP5180, +5V 100K For BT network protection: Note: For CTA applications where there is a requirement to determine the ring burst duration, the value of R and C may have to be optimized. C R

Preliminary Information MT8843 5-31 † DC Electrical Characteristics are over recommended operating conditions unless otherwise stated. Note 1 - Magnitude measurement, ignore signs.

8 TRIGout,

DCLK, DATA, DR, CD , StD, ESt , St/GT TRIGRC , INT Output Low Sinking Current IOL 2.5 mA V OL =0.1*VDD

9 IN+, IN-,

Input Current Iin1 1 µAV in=V DD or VSS See Note 1 PWDN, DCLK, MODE, FSKen Iin2 10 µAV in=V DD or VSS See Note 1

10 TRIGRC Output High-Impedance

Ioz1 1 µAV out =VDD or VSS See Note 111 INT Ioz2 10 µA

12 St/GT Ioz3 5 µA

13 V Ref Output Voltage V Ref 0.5VDD - 0.05 0.5VDD + 0.05 V No Load

14 St/GT Comparator Threshold

VTGt 0.5VDD - 0.05 0.5VDD + 0.05 V Characteristics Sym Min Max Units Test Conditions

Preliminary Information MT8843 5-33 † Electrical characteristics are over recommended operating conditions, unless otherwise stated. ‡ Typical figures are at 25°C and are for design aid only: not guaranteed and not subject to production testing. *Notes 1. Both mark and space have the same amplitude. 2. Band limited random noise (200-3400Hz). Present when FSK signal is present. Note that the BT band is 300-3400Hz, the Bellcore band is 200-3200Hz. † AC Electrical Characteristics are over recommended operating conditions, unless otherwise stated. ‡ Typical figures are at 25°C and are for design aid only: not guaranteed and not subject to production testing. a. dBV = decibels above or below a reference voltage of 1Vrms. b. dBm = decibels above or below a reference power of 1mW into 600 ohms. 0dBm = 0.7746Vrms. Electrical Characteristics† - Gain Setting Amplifier Characteristics Sym Min Typ ‡ Max Units Test Conditions

1 Input Leakage Current I IN 1 µAV SS ≤ VIN ≤ VDD

2 Input Resistance R in 10 M Ω

3 Input Offset Voltage V OS 25 mV

4 Power Supply Rejection Ratio PSRR 40 dB 1kHz ripple on V DD

5 Common Mode Rejection CMRR 40 dB V CMmin ≤ VIN ≤ VCMmax

6 DC Open Loop Voltage Gain A VOL 32 dB

7 Unity Gain Bandwidth f C 0.3 MHz 8 Output Voltage Swing V O 0.5 VDD -0.5 Vpp Load ≥ 50kΩ

9 Maximum Capacitive Load (GS) C L 100 pF

10 Maximum Resistive Load (GS) R L 50 k Ω

11 Common Mode Range Voltage V CM 1.0 VDD -1.0 V Characteristics Sym Min Typ ‡ Max Units Notes*

1 Input Detection Level -40

-37.78 10.0 -5.78 398.1 dBV a dBm b mVrms

2 Transmission Rate 1188 1200 1212 baud

3 Input Frequency Detection

Bell 202 1 (Mark) Bell 202 0 (Space) CCITT V.23 1 (Mark) CCITT V.23 0 (Space) 1188 2178 1280.5 2068.5 1200 2200 1300 2100 1212 2222 1319.5 2131.5 Hz Hz Hz Hz

4 Input Noise Tolerance SNR FSK 20 dB 1,2

Preliminary Information MT8843 5-37 Figure 15 - Input and Output Timing for BT Caller Display Service (CDS), e.g., CLIP Notes: 1) By choosing tGA =15ms, tABS will be 15-25ms so that the current wetting pulse and AC load can be applied right after the StD falling edge. 2) SIN227 specifies that the AC and DC loads should be removed between 50-150ms after the end of the FSK signal, indicated by CD returning to high. The CNIC2 may also be powered down at this time. 3) FSKen should be set low when FSK is not expected to prevent the FSK demodulator from reacting to other in-band signals such as speech, tone alert signal and DTMF tones. 4) TRIGout is the ring envelope during ringing. 5) The total recognition time is tREC = tGP + tDP, where tGP is the tone present guard time and tDP is the tone present detect time (refer to section “Dual Tone Detection Guard Time” on page 25 for details). 6) The total tone absent time is tABS = tGA + tDA , where tGA is the tone absent guard time and tDA is the tone absent detect time (refer to section “Dual Tone Detection Guard Time” on page 25 for details). V TGt is the comparator threshold (refer to Figure 4). Line Reversal Alerting Signal Ch. seizure Mark Data Packet Ring ..101010.. Data tDP tDA tGP tGA tREC tABS (Note 1) 20±5ms tCP tCA AB C D E F G Zss (Refer to SIN227) < 0.5mA (optional)<120µA Note 2 VTGt Note 4 Note 3 A/B Wires TRIGout PWDN ESt St/GT StD TE DC load TE AC load FSKen CD DR DCLK DATA OSCout A ≥ 100ms B = 88-110ms C ≥ 45ms (up to 5sec) D = 80-262ms E = 45-75ms F ≤ 2.5sec (typ. 500ms) G > 200ms Note: All values obtained from SIN227 Issue 1 Note 5 Note 6 50-150ms 15±1ms Current wetting pulse (see SIN227)

Preliminary Information MT8843 5-39 Figure 17 - Input and Output Timing for Bellcore On-hook Data Transmission Associated with Ringing, e.g., CID Notes: This on-hook case application is included because a CIDCW (off-hook) CPE should also be capable of receiving on-hook data transmission (with ringing) from the end office. TR-NWT-000575 specifies that CIDCW will be offered only to lines which subscribe to CID. 1) The CPE designer may choose to enable the CNIC2 only after the end of ringing to conserve power in a battery operated CPE. CD is not activated by ringing. 2) The CPE designer may choose to set FSKen always high while the CPE is on-hook. Setting FSKen low prevents the FSK demodulator from reacting to other in-band signals such as speech, CAS or DTMF tones. 3) The microcontroller in the CPE powers down the CNIC2 after CD has become inactive. 4) The microcontroller times out if CD is not activated. 1st Ring 2nd RingCh. seizure Mark Data Packet AC D E F ..101010.. Data Note 1 Note 2 Note 3 Note 1 Note 4 tCA tCP B TIP/RING TRIGout PWDN OSCout FSKen CD DR DCLK DATA A = 2sec typical B = 250-500ms C = 250ms D = 150ms E = feature specific Max C+D+E = 2.9 to 3.7sec F ≥ 200ms