Icom IC-F21 Service Manual page 11

CPU (IC7)–continued
Pin Port
number name
Input port for the battery's type detec-
61 BDET
tion.
62 BATV Input port for battely voltage detection.
4-5-2 OUTPUT EXPANDER IC (IC15)
Pin Port
number name
Outputs clock shift control signal for
4 CSFT
CPU.
5 RMUT Outputs RX mute control signal.
6 MMUT Outputs TX mute control signal.
Outputs low-pass filter cut-off frequen-
7 DUSE cy control signal when DTCS is acti-
vated.
Outputs T5 regulator control signal.
11 T5C
Low: While transmitting.
Outputs R5 regulator control signal.
12 R5C
Low: While receiving.
Outputs S5 regulator control signal.
13 S5C
Low: While power is ON.
Outputs Narrow/Wide of channel
14 NWC spacing control signal.
Low: While Narrow is selected.
4-5-3 D/A CONVERTOR IC (IC9)
Pin Port
number name
2, 3, Output tunable bandpass filters con-
T1–T4
10, 11 trol signals.
Outputs differential voltage for the ref-
14 REF
erence oscillator (Q31, D19, X1).
15 BAL Outputs DTCS balance control signal.
Outputs modulating signal for the
22 DEV
modulator circuit (D6).
Description
Description
Description
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