Icom IC-756PRO III Service Manual page 17

3-7-3 MAIN-CPU PORT ALLOCATIONS
(MAIN-A UNIT; IC3501)
Pin Port
number name
A0–A3,
6–9,
Address signal output ports for the
A4–A11,
11–18,
LCD controller (IC3551).
A12–A18
20–26
Input port for the [KEY] jack.
SKYS
29
Low : During key down
RTKI Input port for the RTTY keying.
30
Power supply detection input port for
DPGI
31
the DSP-A board.
Input port for data signal from DSP-A
DSDR
32
board.
Input port for the [POWER] switch.
PWRK
34
Low : When the [POWER] is pushed.
DSKY Outputs CW/RTTY keying.
37
DB0–DB3, Data bus lines for the LCD controller
40–43,
DB4–DB11, (IC3551) and I/O expander (IC3652–
45–52,
DB12–DB15 IC3654).
54–57
CTXD Outputs the CI-V signal.
59
CRXD Input port for the CI-V signal.
61
MCK Outputs clock signal.
63
MDAT Outputs data signal.
64
Input port for the [XVERT] detection
TRVI
66
signal.
Input port for transmit control signal
IKEY from the antenna tuner CPU (CTRL-A
69
board; IC5).
Outputs R8V regulator (Q601, Q602,
RXS D601) control signal.
70
Low : While receiving
Outputs T8V regulator (Q611, Q612,
TXS D611) control signal.
71
Low : While transmitting
ISTA Outputs antenna tuner start signal.
72
Outputs reset/inhibit signal to the sub-
CPU (DISPLAY board; IC401), DDS
DRES ICs (PLL unit; IC101, IC401), antenna
73
tuner CPU (CTRL-A board; IC5), and
etc.
Input port for unlock signal from the
UNLC
74
PLL unit.
Outputs strobe signals for the I/O
PSTB
75
expander IC (PLL unit; IC1).
Outputs strobe selection signals for
PSEL
76
the I/O expander (PLL unit; IC1).
Outputs control signal for the DDS cir-
CON2
77
cuits (PLL unit; IC101, IC401).
Description
Pin Port
number name
CON1
78
(PDAT)
CON0
79
(PCK)
XTAL,
85, 86
EXTAL
LRES
96
LTXD
97
LRXD
98
TMD
101
SCPL
105
VOXL
106
AVXL
107
ASO0
108
ASO1
109
ASO2
110
STON
111
BEEP
112
SENI
115
PWRS
116
3 - 11
Description
Outputs data signal for the DDS cir-
cuits (PLL unit; IC101, IC401).
Outputs clock signal for the DDS cir-
cuits (PLL unit, IC101, IC401).
Input ports for the CPU system clock
oscillator (X3501; 19.6608 MHz).
Outputs reset/inhibit signal for the
LCD controller (IC3551), I/O expander
(IC3652–IC3654), and etc.
Outputs data signal for the sub-CPU
(DISPLAY board; IC401).
Input port for data signal from the
sub-CPU (DISPLAY board; IC401).
Outputs [TIMER] indicator control sig-
nal.
High : When the timer function is ON
Input port for the scope signal.
A/D input port for the VOX gain.
A/D input port for the anti-VOX level.
A/D input port via the analog switch
(IC3631) for the SML signal from the
S-meter amplifier circuit (IC101a),
and ALCL signal from the ALC meter
amplifier circuit (IC551a).
A/D input port via the analog switch
(IC3631) for the NSQO signal from
the level conveter (DSP-A board;
IC2063), for noise squelch opera-
tion, and FORL signal from the power
meter amplifier circuit (IC571a).
A/D input port from the analog switch
(IC3631) for the FNTL signal from
the low-pass filter (DSP-A board;
IC2472a), for tone squelch operation,
and REFL signal from the SWR meter
amplifier circuit (IC571b).
Outputs CW side-tone signals.
Outputs beep audio signals.
Input port for connected microphone's
PTT switch and SEND signal from the
ACC jacks.
High : While PTT switch is pushed or
activated from an external unit.
Outputs control signal for the power
switching relay (PA unit; RL1) .
High : During power ON