Icom IC-M502 Service Manual page 13

4-7-2 MAIN CPU (MAIN unit; IC16)
Pin Port
number name
Outputs control signal to the analog
switch (IC12) for passing through the
1 STRU
optional VOICE SCRAMBLER unit
(UT98 or UT-112).
Outputs ON/OFF control signal for the
2 SCON optional VOICE SCRAMBLER unit
(UT-98 or UT-112).
Outputs strobe signals for the optional
3 OPSTB VOICE SCRAMBLER unit UT-98 or
UT-112.
Outputs strobe signals to PLL IC (IC2,
4 PSTB
pin 2).
Outputs clock signal to PLL IC (IC2,
5 CK
pin 3).
Outputs clock signal to PLL IC (IC2,
6 DATA
pin 4).
Outputs main microphone (HM-126)
7 PTTM select signal to the analog switch
(IC10) while intercom operation.
Outputs optional remote microphone
8 PTTS (HM-127) select signal to the analog
switch (IC10) while intercom operation.
Outputs select signal for the speaker
of main microphone (HM-126) to the
10 MMUTE
analog switch (IC10) while intercom
operation.
Outputs select signal for the speaker
of optional remote microphone (HM-
11 SMUTE
127) to the analog switch (IC10) while
intercom operation.
Outputs ON/OFF control signal for the
internal speaker to the AF mute circuit
12 SP
(Q32, D23, RL2).
Low : While internal speaker is ON.
Output port for RF output power (High
13 HI/LO or Low) select signal.
Low : While low power is selected.
Outputs the T8 regulator (Q20, Q21)
14 SEND control signal.
Low : While transmitting
Outputs transmit mute signal.
15 TMUTE
High : While transmitting
Input port for the communication data
16 SRXD
from sub CPU (LOGIC unit; IC1).
Outputs communication data for sub
17 STXD
CPU (LOGIC unit; IC1).
Input port for the cloning data from the
19 CLRX
buffer (D24).
Description
Pin Port
number name
20 CLTX
23 ECK
24 EDA
27 MICDSC
30 DSC
39 SQL
42 LBAT
44 TXDET
45 DSDEC
46 UNLK
60 PTT
61 HANG
62 OPTIN
66 RCV
67 RMUTM
68 RMUTS
69 BEEPM
71 BPLVM
75 RESET
100 SRESET
4 - 5
Description
Output port for the cloning data to the
buffer (MAIN unit; Q37).
Outputs clock signal for EEPROM
(IC17).
Outputs serial data signal for EEP-
ROM (IC17).
Outputs select signal to the analog
switch (IC12) for the microphone audio
signal or DSC signal.
D/A output port for the ATIS/DSC
encode signal to the buffer amplifier
(Q33).
Input port from the FM IF IC (IC1) for
the squelch operation.
Input port for the connected power
supply voltage detection (low battery
indicator).
Input port for the "TX" indicator from
the power detector circuit (D14, D15).
Input port for the ATIS/DSC decode
signal.
Input port for the PLL unlock signal.
Low : While PLL is locked.
Input port for the PTT switch.
Input port for the microphone hanger
detection signal.
Low : Microphone on hook
Input port for the optional unit connec-
tion detection.
Outputs the R8 regulator (Q22, Q23)
control signal.
Low : While receiving
Outputs the AF mute switch (Q26)
control signal for main body.
Low : While squelched
Outputs the AF mute switch (Q27)
control signal for the optional remote
microphone (HM-127).
Low : While squelched
Outputs beep audio for main body.
Outputs beep audio for the optional
remote microphone (HM-127).
Input port for the reset signal.
Outputs the reset signal for sub CPU
(LOGIC unit; IC1).