Icom IC-M88 Service Manual page 12

CPU–Continued
Pin Port
number name
Input port for the [DOWN] key.
111 DOWN
Low : While [DOWN] key is pushed.
Input port for the [CH/WX] key.
112 CH/WX
Low : While [CH/WX] key is pushed.
Input port for the [16/9] key.
113 16/9
Low : While [16/9] key is pushed.
Input port for the [SCAN] key.
114 SCAN
Low : While [SCAN] key is pushed.
Input port for the [H/L] key.
115 H/L
Low : While [H/L] key is pushed.
Outputs decode monitor signal to
116 TDEC
CP641 on the LOGIC unit.
Input port for the PLL unlock signal.
119 UNLK
High : PLL lock voltage is unlocked.
Description
4-5-2 EXPANDER IC (MAIN UNIT; IC341)
Pin Port
number name
5 SRXMS
6 DETMS
7 CKSIS
11 ATTS
12 TXMS
13 VCOS
4-5-3 D/A CONVERTOR IC (MAIN UNIT; IC251)
Pin Port
number name
2 SQCON
3 MOCON
10 DTCON
11 FRCON
14 T1CON
15 T2CON
22 T3CON
23 T4CON
4 - 5
Description
Outputs the AF mute switch (IC281,
pin 3) control signal.
Low : While the scrambler decord-
ing signal is muted.
Outputs the AF mute swtich (IC281,
pin 7) control signal.signal.
Low : While AF signal is muted.
Outputs the scrambler IC's clock shift
control signal.
High : While the clock is shifted.
Outputs the RF attenuator control sig-
nal.
High : While attenuator is ON.
Outputs the TX mute swtich (Q141)
control signal.
Low : While TX is attenuated.
Outputs the TX/RX VCO control sig-
nal.
Description
Outputs squelch level control signal.
Outputs modulatin level control signal.
Outputs DTCS modulation balance
control signal.
Outputs reference frequency level
control signal.
Outputs bandpass filter1 tuned and
transmitting power control signals.
Outputs bandpass filter2 tuned signal.
Outputs bandpass filter3 tuned signal.
Outputs bandpass filter4 tuned signal.