Codan NGT 2010 RF Technical & Service Manual page 725

3012—Technical description
DSP Modem PCB
The DSP Modem PCB comprises a 32-bit DSP and associated memory, interfacing and
power supply components.
Digital signal processor and CoDec
Drawings
A Texas Instruments TMS320C31 32-bit floating-point DSP (IC101) forms the heart of
the data modem. It is interfaced to the transceiver transmit and receive audio paths via a
CoDec (IC108), input differential amplifier (stages IC109/A and IC109/B), and audio
isolation transformers (T101 and T102).
The CoDec (IC108) is an ADC/DAC, which interfaces to the DSP via a serial interface,
using frame strobe and clock signals.
A watchdog/power on/reset IC (IC102) ensures that the DSP is held in reset until the
power supply rails have stabilised, and also serves to reset the processor if unexpected
code run-away stops the strobe line from being regularly toggled.
Memory
Drawings
The program code for the data modem is stored in two 2 Mbit EPROMs (IC202/204),
each organised as 128 k by 16-bit words. These are paralleled to create an effective 128 k
of 32-bit memory.
The data modem also requires external SRAM, which is provided by devices IC201 and
IC203. Each 128 k by 16-bit device is paralleled to provide a 128 k by 32-bit memory.
A small amount of non-volatile data storage is provided by a 2 kbit (256 by 8-bit)
EEPROM (IC205), which is accessed serially using a 2-wire I
interface.
Logic and interfacing
Drawings
A 32-Macrocell programmable logic device (IC106) performs the 'glue logic' required
to perform several functions, including:
•
•
•
IC107 is a complex device, which features two complete serial communication interfaces
with 16-byte FIFOs and an additional parallel port. The primary role of IC107 is to
provide the serial interface between the RS232 interface of the data terminal equipment
and the DSP.
304
04-03366 (sheet 1)
04-03366 (sheet 1)
04-03366 (sheet 1)
decoding the memory span of IC101 into the format required by the firmware
generating read, write and chip-select signals for the memory devices
inverting the interrupt request signals produced by a dual asynchronous
communications element (IC107)
and 04-03366 (sheet 2)
and 04-03366 (sheet 2)
and 04-03366 (sheet 2)
NGT Transceiver System Technical Service Manual
2
C-compatible serial