4-4-3 CPU (LOGIC UNIT)
The CPU (IC1) contains an 8-bit CMOS CPU, a 60 k-byte
ROM, a 2 k-byte RAM. A 9.8304 MHz clock is used for rapid
operation. The CPU controls the operating frequency, mode,
function display, etc. The memory channel information is
stored in the EEPROM (IC2).
The Icom CI-V network system allows the IC-78 to be
remotely controlled by a personal computer using an RS-
232C I/O port.
4 - 7
• PORT ALLOCATIONS (LOGIC unit; IC1)
1
11, 13
15–17
18
19
21
22
23
24
25
26
41, 42
43
52
54
55
57
58
Input port for the anti-VOX voltage.
Input port for [MAIN DIAL] up/down
signals.
Output control bit signals for the 1st
LO DDS circuit (PLL unit; IC6).
Output reset signal for the DDS cir-
cuits (PLL unit; IC2, IC6) and D/A con-
verters (MAIN unit; IC3001, IC3004,
IC3006), etc.
Outputs serial clock signal for the DDS
circuits (PLL unit; IC2, IC6).
Outputs serial data signals for the
DDS circuits (PLL unit; IC2, IC6).
Outputs strobe signals for the 1st LO
DDS circuit (PLL unit; IC6).
Outputs strobe signals for the BFO
DDS circuit (PLL unit; IC2).
Outputs strobe signals for the D/A con-
verter (MAIN unit; IC3001).
Outputs strobe signals for the D/A con-
verter (MAIN unit; IC3004).
Outputs strobe signals for the D/A con-
verter (MAIN unit; IC3006).
Output LCD backlight control signals
for the dimmer circuit (Q70–Q72).
Outputs squelch mute control signal,
applied to the AF selector switch
(MAIN unit; IC2102).
High : Squelch opens
Outputs control signal for the alarm cir-
cuit (MAIN unit; Q2201).
Outputs serial clock signal for the I/O
expander (MAIN unit; IC3301) and D/A
converters (MAIN unit; IC3001,
IC3004, IC3006).
Outputs serial data signals for the I/O
expander (IC3301) and D/A converters
(IC3001, IC3004, IC3006) on the
MAIN unit.
Outputs start signal for the optional
antenna tunner.
Input port for transmit control signal
from the optional antenna tunner CPU.
AVXL
SEN1,
SEN2
CON0–
CON2
DRES
PCK
PDAT
DSTB
PSTB
BSTB
FSTB
MSTB
P55,
P56
SQLS
ALMS
MCK
MDAT
STAT
KEY
Pin
Port
Description
number
name
LOGIC unit; IC1
60
61
62
63
70
71
77
79
80
81
82
85
86
87
88
90
91
92
93
95
96
97
98
99
100
Outputs chip select signal for EEP-
ROM (IC2).
Input port for serial signal from EEP-
ROM (IC2).
Outputs serial signal to EEPROM
(IC2).
Outputs serial clock signal to EEP-
ROM (IC2)
Input port for [KEY] jack, dash signal.
Low : During key down.
Input port for [KEY] jack, dot signal.
Low : During key down.
Outputs switching relay (PA unit; RL1)
control signal.
Outputs beep/CW side tone/alarm
audio signals.
Outputs R8V regurator (MAIN unit;
IC3005) control signal.
Low : While receiving.
Outputs T8V regurator (MAIN unit;
IC3005) T13V regurator (MAIN unit;
Q3801, Q3802) control signal.
Low : While transmitting.
Input port for the [POWER] switch.
Low : While [POWER] is pushed.
Outputs strobe signals for the I/O
expander (MAIN unit; IC3301).
Input port for the CI-V control signals.
Outputs CI-V control signals.
Input port for connected microphone’s
PTT switch and SEND signal from the
[ACC] jack.
Low : While the PTT is pushed or
activated from an external
unit.
A/D input port for the [AF] control.
A/D input port for the [RF/SQL] control.
A/D input port for the [RIT] control.
A/D input port for the [SHIFT] control.
A/D input port for the microphone
up/down signal.
A/D input port for the SWR detector
circuit (FILTER unit; D2).
A/D input port for the SWR detector
circuit (FILTER unit; D3).
A/D input port for the S-meter amplifier
circuit (MAIN unit; IC1701d).
A/D input port for the ALC meter ampli-
fier circuit (MAIN unit; IC1751a).
A/D input port for the VOX voltage.
ECS
ESI
ESO
ESCK
DASK
DOTK
POWS
BEEP
RXS
TXS
PWRK
ASTB
P41
P42
SEND
AFGL
RFGL
RITL
SFTL
UD
FORL
REFL
SML
ALML
VOXL
Pin
Port
Description
number
name
