Digital Signal Processor (Dsp) - Tait TB8100 Service Manual

2.1.2

Digital Signal Processor (DSP)

Transmit Functions
Receive Functions
Serial Ports
30 Reciter Circuit Description
The DSP is responsible for software processing of digitised signals in the
receiver and transmitter. The processing word width is 16-bit fixed point.
There are 96 kilobytes of on-chip program memory, and 64 kilobytes of
on-chip data memory. Although no external memory is used, the external
memory interface is connected to the DDC for initialisation and
configuration.
The DSP performs the following transmit functions:
CTCSS and DCS sub-audible signal generation
CWID generation
pip tone generation
audio filtering: including removal of sub-audible components, pre-
emphasis and low pass filtering
signal path switching
signal level adjustment
peak FM deviation limiting
FM signal generation by controlling the dual point modulator
calibration parameter estimation
line level monitoring.
The DSP performs the following receive functions:
detection of CTCSS and DCS signalling
audio filtering: including removal of sub-audible components, de-
emphasis and low pass filtering
signal path switching
signal level adjustment
FM demodulation of the base band signal
RSSI measurement for monitoring and RSSI signal voltage output
SINAD measurement
measurement and detection for control of the audio mute
calibration parameter estimation
line level monitoring.
The DSP has three synchronous serial ports. Serial port 1 is connected to
the DDC and receives base band samples. Serial port 2 is connected to the
three CODECs (encoder/decoder). Serial port 3 is not used.
TB8100 Service Manual
© Tait Electronics Limited September 2006