Controller Board Audio And Signalling Circuits; General - Audio Signalling Filter Ic With Compander (Asfic Cmp); Transmit Audio Circuits - Motorola GM328 Service Manual

Controller Board Audio and Signalling Circuits

2.0 Controller Board Audio and Signalling Circuits
2.1

General - Audio Signalling Filter IC with Compander (ASFIC CMP)

The ASFIC CMP (U0221) used in the controller has 4 functions;
1) RX/TX audio shaping, i.e. filtering, amplification, attenuation
2) RX/TX signalling, PL/DPL/HST/MDC/MPT
3) Squelch detection
4) Microprocessor clock signal generation (see Microprocessor Clock Synthesizer Description).
The ASFIC CMP is programmable through the SPI BUS (U0221-20/21/22), normally receiving 19
bytes. This programming sets up various paths within the ASFIC CMP to route audio and/or
signalling signals through the appropriate filtering, gain and attenuator blocks. The ASFIC CMP also
has 6 General Control Bits GCB0-5 which are CMOS level outputs and used for NOISE BLANKER
(GCB0) in Low Band radios, EXTERNAL ALARM (GCB1) and DC POWER ON (GCB2) to switch
the voltage regulators (and the radio) on and off. GCB3 controls U0251 pin 11 to output either RX
FLAT AUDIO or RX FILTERED AUDIO on the accessory connector pin 11. GCB4 controls U0251
pin 10 to use either the external microphone input or the voice storage playback signal. GCB5 is
used to switch the audio PA on and off.
2.2

Transmit Audio Circuits

Refer to Figure 1-3 for reference for the following sections.
FLAT
TX RTN
EXPANSION BOARD
MIC
CONTROL HEAD
EXT MIC
FLAT TX
AUDIO
J0451
18
J0401
TP0221
9
CONNECTOR
J0501
TP0222
2
5
U0211-4
ACCESSORY
FROM
CONNECTOR
µP Pin3
Figure 1-3 Transmit Audio Paths
31 IN/OUT
39
OUT
33
IN
44
TX SND
MIC
INT
46 FILTERS AND
PREEMPHASIS
ASFIC_CMP
MIC
IN
U0221
LIMITER
MIC
EXT
48
HS SUMMER
42
SPLATTER
FILTER
AUX
TX
LS SUMMER
J0551
OPTION
BOARD
OUT
32
36
TX RTN
VCO
MOD IN
TO
ATN
40
RF
SECTION
(SYNTHESIZER)
ATTENUATOR
1-11