Other Circuits; Power Supply Circuits; Port Allocations - Icom IC-M72 Service Manual

4-4 OTHER CIRCUIT
4-4-1 VOX CIRCUIT (MAIN UNIT)
The VOX circuit toggles TX and RX automatically by detect-
ing voice signals from the microphone.
The MIC signals from the external microphone are applied
to the VOX amplifier (IC431, pins 1, 2). The amplified MIC
signals are applied to another VOX amplifier (IC431, pin 5),
and the amplified MIC signals are output from pin 7, then
rectified by D430. The rectified signal is applied to the CPU
(IC360, pin 29) as "VOXT" signal which turns the transmit
circuits ON. Then the CPU outputs "VOXM" signal from pin
117 to the AF mute switch (IC430, pin 5) to turn the AF
mute switch OFF, and the MIC signals are applied to the
pre-emphasis circuit.

4-5 POWER SUPPLY CIRCUITS

(MAIN UNIT AND RF UNIT)
Line
name
VCC The same voltage as attached battery pack.
Common 5 V converted from VCC line at the
CPU5V regulator (IC220).
CPU5V
The converted voltage is applied to the CPU
(IC360), Reset IC (IC341), EEPROM (IC340), etc.
Common 5 V converted from VCC line at the 5V
regulator (Q223−Q225) controlled by "M5VS" signal
from CPU (IC360, pin 101).
5V
The converted voltage is applied to the backlight
LED'S (DS240−DS243, DS250−DS253), D/A con-
verter (RF UNIT; IC190), PLL IC (RF UNIT; IC1), etc.
Common 5 V converted from VCC line at the V5V
regulator (RF UNIT; Q220).
V5V
The converted voltage is applied to the VCO (RF
UNIT; Q21, Q22, D21−D23)
Receive 5 V controlled by R5V regulator (Q221)
using "R5VS" signal from the CPU (IC360, pin 95).
R5V The voltage is applied to the receive circuits (RF
UNIT; 1st mixer (Q150), 1st IF amplifier (Q151),
RF amplifi er (Q90), etc.).
Transmit 5 V controlled by T5V regulator (RF UNIT;
Q222) using "T5VS" signal from the CPU (IC360,
pin 13).
T5V The controlled voltage is applied to the transmit
circuits (RF UNIT; differential amplifi er (IC50), pre-
driver (Q53), power amplifier (Q54), microphone
amplifi er (IC8), etc.).
Description

4-6 PORT ALLOCATIONS

4-6-1 CPU (MAIN UNIT; IC360)
Pin Port
No. Name
1 BEEP Outputs beep sound to the AF circuits.
DASTB Outputs strobe signal to the D/A converter (RF
4
(DAST) UNIT; IC190, pin 6).
PLSTB
Outputs PLL strobe signal to the PLL IC (RF
5
UNIT; IC1, pin 3).
(PLST)
Outputs serial crock signal to the PLL IC (RF
SCLK
11 UNIT; IC1, pin 4), D/A converter (RF UNIT;
(SCK)
IC190, pin 7).
Outputs V5V regulator (Q220) control signal.
"High"= While power save mode (The VCO
12 V5VS
(Q21, Q22, D21−D23)
Outputs T5V regulator (RF UNIT; Q222) control
signal.
13 T5VS
"Low"= While transmitting.
"High"= While receiving or power save mode.
Outputs LCD contrast select signal.
14 LCDS "Low"= While "Bright" is selected.
"High"= While "Dark" is selected.
Outputs backlight LED (DS240
15 LEDS DS253) control signal to the LED driver (Q240).
"High"= While the backlight is ON.
Input port for reset signal from the reset IC
25 RES
(IC341, pin 1).
Input port for demodulated weather alart (WX)
†
27 WDECV
signal from the AF circuits.
28 EXDET Input port for external connect detect signal.
Input port for audio detect signal from the VOX
29 VOXT
amplifi er (IC431, pin 7) for the VOX operation.
30 BATTV Input port for remaining battery power.
Input port for power level detect signal from the
31 TDETV
transmit power detector (RF UNIT; D80).
Inputo port for the noise level from the FM IF IC
32 NOISV
(IC170, pin 14).
Input port for RSSI signal from the FM IF IC
33 RSSIV
(IC170, pin 12).
Input port for VCO (
34 LOINV
voltage.
35 TEMPV Input port for temperture detection.
36 WET Input port for leaking detection signal.
Outputs serial crock signal to the EEPROM
93 ESCK
(IC340, pin 6).
94 ESDA Outputs serial data to the EEPROM (IC340, pin 5).
Output R5V line control signal to the R5V
95 R5VS regulator (Q221).
"High"= While receiving.
Input port for external PTT switch.
96 EXPTT
"High"= While the external PTT switch is pushed.
Outputs transmit mute signal to the transmit
97 TXMS mute switch (Q351).
"High"= While transmitting.
Outputs mute signal to the AF mute switch
98 DETMS (IC260, pin 13).
"High"= While the squelch is open.
Outputs AF power amplifier power supply
switch control signal.
100 AFVS
"High"= While the audio is emitted from the internal
speaker (CHASSIS; SP1) or external speaker.
Input port for [PTT] switch. (RF UNIT; S250)
102 PTTIN
"High": While [PTT] switch is pushed.
4 - 4
Description
is not activated).
− −
DS243, DS250
Q21, Q22, D21−D23 ) lock
†
; ([USA], [USA-01] only)