![background image](http://html2.mh-extra.com/html/icom/ic-f620/ic-f620_service-manual_3734180011.webp)
4 - 5
CPU (IC20)—continued
CPU (IC20)—continued
Input port for MIC mute signal from the
optional board via J1.
I/O ports for the optional board control
signals.
NOIS signal input port from the FM IF
IC (MAIN unit; IC1) for noise squelch
operation.
Input for the POWER switch.
Low : While POWER switch is pushed.
Input port for DTMF detection signal
from the DTMF decoder (IC19).
Remote power control signal input port
from the external connector (J8).
Outputs control signal for the power
switching circuit (Q24, Q23) via D28.
Outputs single tone signal.
Outputs beep audio signals.
Single tone signal input port for decod-
ing from the LPF (IC21c).
CTCSS/DTCS signals input port for
decoding from the LPF (IC5).
Input port for the PLL unlock signal
from the PLL IC (IC4).
Input port for the overvoltage detection
from the connected power supply.
Input port for the PLL lock voltage.
Input port for receiving signal strength
level detection.
Input port for the transceiver’s internal
temperature.
Input port for the AF volume control
(FRONT unit; R12).
High : [VOL] is maximum clockwise.
Input port for the PTT switch from the
external connector (J6).
Low : External PTT switch is ON.
Input port for the reset signal.
Output port for the cloning signal.
Input port for the cloning signal.
Outputs CPU clock shift signal.
Outputs cut-off frequency control signal
to the low-pass filter (IC5) for
CTCSS/DTCS switching.
Input port for the connected modem
unit via external connector (J9).
Output port for the connected modem
unit via external connector (J9).
33
34–36
37
38
39
40
41
43
44
45
46
47
48
49
50
51
52
55
59
68
69
70
71
74
75
MMUT
OPT1–
OPT3
NOIS
POSW
DDST
IGSW
PWON
SENC
BEEP
SDEC
CDEC
ULCK
BATV
LVIN
RSSI
TEMP
AFVI
EPTT
RES
CLO
CLI
CSFT
DUSE
XCTS
XRTS
Pin
Port
Description
number
name
Input port for serial data signals from
the connected MAP27 unit via external
connector (J9).
Outputs serial data signals for the con-
nected MAP27 unit via external con-
nector (J9).
Output serial data signals (data format
is in accordance with NMEA0183) for
the connected unit via external connec-
tor (J8).
Input port for serial data signals (data
format is in accordance with
NMEA0183) from the connected unit
via external connector (J8).
Input port for interruption signal from
the optional board via J1
Input port for the LCD backlight control
signal from the external connector (J6).
Output ports for the CTCSS/ DTCS sig-
nals.
Outputs reset signal for the compander
IC (IC14).
Output control signals for the compan-
der IC (IC14).
Outputs strobe signals to the compan-
der IC (IC14).
Outputs control signal for the MSK
PM/FM switching circuit (IC15).
I/O port for the data signals from the
EEPROM (IC23).
Outputs clock signal for the EEPROM
(IC23).
Outputs MIC audio select signal for the
analog switch (IC25).
Low : While “Public-address” function
is ON.
76
77
79
80
81
88
89–91
92
94,
95
96
97
98
99
100
XTXD
XRXD
NTXD
NRXD
CIRQ
DIM
CENC2–
CENC0
AFCL
AMSK,
ADIN
APST
PMFM
ESDA
ESCL
PA
Pin
Port
Description
number
name