Icom IC-F21 CPU IC7-continued, OUTPUT EXPANDER IC IC15, 4-5-3 D/A CONVERTOR IC IC9, Port, number

CPU (IC7)–continued

Pin	Port	Description
number	name
61	BDET	Input port for the battery’s type detec-
		tion.
62	BATV	Input port for battely voltage detection.

4-5-2 OUTPUT EXPANDER IC (IC15)

Pin	Port	Description
number	name
4	CSFT	Outputs clock shift control signal for
		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.
11	T5C	Outputs T5 regulator control signal.
		Low: While transmitting.
12	R5C	Outputs R5 regulator control signal.
		Low: While receiving.
13	S5C	Outputs S5 regulator control signal.
		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	Description
number	name
2, 3,	T1–T4	Output tunable bandpass filters con-
10, 11		trol signals.
14	REF	Outputs differential voltage for the ref-
		erence oscillator (Q31, D19, X1).
15	BAL	Outputs DTCS balance control signal.
22	DEV	Outputs modulating signal for the
		modulator circuit (D6).

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