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