User Guide

PAMS
System Module DB6
NHB–3
Technical Documentation
Original 26/97
Page 4–27
Block Description
The Control unit communicates with the DSP circuitry through a mailbox in the
D2CA ASIC. The software for the external memories are loaded through this
mailbox in start up.
The DSP includes two serial busses. One is used for speech data transfer be-
tween the DSP and the codec. The other is used as an external data bus and it
is connected to the system connector. This bus can be used by data accesso-
ries and also as a digital audio interface (DAI) in audio type approval measure-
ments. The clocks (512 kHz main clock and 8 kHz sync. clock) are generated
by the ASIC.
In transmit mode the DSP codes the speech and routes the resulting transmit
slots to the D2CA. The D2CA ASIC controls timing, and at specified intervals
sends these bits to the RFI for DA conversion.
In digital receive mode the RFI AD converts the IF signal from the RF unit un-
der the control of the D2CA. The DSP controls the D2CA and receives the con-
verted bits. After channel and speech decoding, bits are converted into an ana-
log signal in the PCM codec, routed and fed to the earpiece.
The DSP controls the RF through the D2CA ASIC, where all necessary timing
functions are implemented, and control I/O lines are provided eg. for synte
loading.
The DSP emulator can be connected to pins TCK, TMS, TDO, TDI, GND, VDD
Main Components
– AT&T DSP1616–S11
Digital signal processor with 12kword internal ROM
– Two 32k *8 70ns SRAMs for DSP external memory
– 60.2 MHz crystal oscillator to generate differential small signal clock for the
DSP, clock enable come from ASIC