Download User Manual

Component Product Manual
11/6/2003
AT&T source files: b103.s, b103.inc, b103.h.
This 2-channel modem operates at a data-signaling rate of 300 bit/s with a symbol rate of 300 symbols/sec.
The modulation method is continuous phase frequency shift keying (CP-FSK). The demonstration code
provides a working example of a Bell 103 modem. If run on a target platform, such as a TI DSK5402, the
demonstration code will initialize the transmit and receive sections of the modem and wait for a call on the
DAA. It will then answer the call and link to another Bell 103 modem looping back all characters received.
If the DIGITAL_LOOPBACK option is enabled at build time, the demonstration code, will provide a
digital loopback of the Tx sample output to the Rx sample input. The contents of the Rx_block[] can be
examined to compare with the Tx_block[].
6.2.1 AT&T Compliance:
The modem is fully compliant with all sections of Bell System Technical Reference PUB 41101, Data Set
Interface Specification 103A.
6.2.2 Applications Programmer Interface Functions and Macros
void Tx_init_bell103_F1(struct START_PTRS *) - Configures Tx_block[] for Bell 103 channel 1
transmitter (modulator) operation, and sets the Tx->state to Tx_bell103_message.
void Tx_init_bell103_F2(struct START_PTRS *) - Configures Tx_block[] for Bell 103 channel 2
transmitter (modulator) operation, and sets the Tx->state to Tx_bell103_message.
void Rx_init_bell103_F1(struct START_PTRS *) - Configures Rx_block[] for Bell 103 channel 1
receiver (demodulator) operation, and sets the Rx->state to Rx_bell103_message.
void Rx_init_bell103_F2(struct START_PTRS *) - Configures Rx_block[] for Bell 103 channel 2
receiver (demodulator) operation, and sets the Rx->state to Rx_bell103_message.
6.2.3 Transmitter States (by STATE_ID)
TX_BELL103_F1_MESSAGE_ID – Channel 1 data transmission state.
TX_BELL103_F2_MESSAGE_ID – Channel 2 data transmission state.
6.2.4 Receiver States (by STATE_ID)
RX_BELL103_F1_MARKS_ID – Detect Marks pattern on channel 1.
RX_BELL103_F1_MESSAGE_ID - Demodulate data symbols on channel 1 and sink to Rx_data[].
RX_BELL103_F2_MARKS_ID – Detect Marks pattern on channel 2.
RX_BELL103_F2_MESSAGE_ID - Demodulate data symbols on channel 2 and sink to Rx_data[].
6.3
Bellcore 202 modem
Simulator source files: bell202.c, bell202.h.
Texas Instruments source files: bell202.asm, bell202.inc, bell202.h.
Analog Devices source files: bell202.dsp, bell202.inc, bell202.h.
AT&T source files: bell202.s, bell202.inc, bell202.h.
The Bell 202 modem is a 2 channel modem with a channel data signaling rate of 600, 1200 and 1350 bit/s
with symbol rates of 600, 1200 and 1350 symbols/sec. The modulation method is continuous phase
frequency shift keying (CP-FSK). The demodulator does not include any preamble detection or training – it
simply demodulates and dumps the data in Rx_data[]. For optimum performance the user should provide a
detector for the start of a Bell 202 modulated burst (such as in the Caller ID case) and then initialize the
demodulator.
6.3.1 AT&T Compliance:
The modem is fully compliant with all sections of AT&T Bulletin, Data Set 202 Interface Specification.
29