Icom IC-F521 Service Manual

4 - 6
4-6-3 CPU (MAIN UNIT; IC2)
Pin
number
Port
name
Description
1 DSDA
I/O port for data signal to the D/A con-
verter (IC7).
2 DAST
Outputs strobe signals to the D/A con-
verter (IC6).
8, 9
LINH,
LCS
Output LCD control signals to the
LCD driver (FRONT unit; IC1).
10 LSCK
Outputs clock signal to the LCD driver
(FRONT unit; IC1).
11 LSO
Outputs data signal to the LCD driver
(FRONT unit; IC1).
13 PLST
Outputs strobe signal to the PLL IC
(IC4).
16 TXC
Outputs the R8 regulator circuit (Q26,
Q30, D24) control signal.
Low: During receive.
17 TMUT
Outputs the T8 regulator circuit (Q25,
Q29, D23) control signal.
Low: During transmit.
18 AFON
Outputs control signal for AF mute cir-
cuit (Q39, Q40, D31).
High: While AF amplifier (IC8) is
activated.
19 NWC
Outputs IF band width control signal.
High: While IF bandwidth is nar-
row.
20 DDSD
Input port for data signal from the
DTMF decoder IC (IC19, pin 9).
21 DDAC
Outputs clock signal to the DTMF de-
coder IC (IC19, pin 10).
22 SO
Outputs data signal to the PLL IC
(IC4), D/A converter (IC6), compand-
er IC (IC14) and optional unit (connect
to J1), etc.
23 SI
Input port for clock signal from the op-
tional unit via J1.
24 SCK
Outputs clock signal to the PLL IC
(IC4), D/A converter (IC6), D/A con-
verter (IC7), compander IC (IC14) and
optional unit (connect to J1), etc.
25 CCS
Outputs chip select signal for the op-
tional unit via J1.
26–28
KR0–
KR2
Input ports for the programmable
function keys (P0–P4, , , , ).
29 PTTO
Input ports for the PTT switch from
the optional unit via J1.
Low: External PTT switch is ON.
30 HANG
Input port for the microphone hanger
detection signal.
Low: When microphone is on the
hook.
31 BUSY
Outputs BUSY detection signal for the
optional unit via J1.
32 RMUT
Input port for the AF mute signal from
the optional unit via J1.
Low: While RX audio is muted.
Pin
number
Port
name
Description
33 MMUT
Input port for the microphone mute
signal from the optional unit via J1.
Low: The microphone audio is
muted.
34–36
OPT1–
OPT3
I/O ports for the optional unit.
37 NOIS
Input port for the noise signal from the
FM IF IC (IC1, pin 13).
38 POSW
Input port for the [ ] switch.
Low: The [ ] switch is pushed.
39 DDST
Input port for DTMF detection signal
from the DTMF decoder IC (IC19).
40 IGSW
Input port for the remote power con-
trol signal from external connector
(J8).
41 PWON
Outputs control signal for the power
switch circuit (Q23, Q24) via D28.
High: While power ON.
43 SENC Output single tone signal.
44 BEEP Outputs beep audio signal.
45 SDEC
Input port for single tone signal from
the LPF (IC21, pin 8).
46 CDEC
Input port for CTCSS/DTCS signal
from the LPF (IC5, pin 1).
47 ULCK
Input port for the PLL unlock signal
from the PLL IC (IC4).
Low: The PLL circuit is unlocked.
48 BATV
Input port for the connected battery
for the low battery detection.
49 LVIN Input port for the PLL lock voltage.
50 RSSI
Input port for the S-meter signal from
the FM IF IC (IC1, pin 12).
51 TEMP
Input port for the transceiver’s internal
temperature detecting signal.
52 AFVI
Input port for the AF volume control
(FRONT unit; R12).
High: [AF VOLUME] is maximum
clockwise.
55 EPTT
Input port for the PTT switch from the
external connector (J6).
Low: External PTT switch is ON.
59 RES Input port for the reset signal.
68 CLO Outputs the cloning signal.
69 CLI Input port for the cloning signal.
71 DUSE
Outputs cut-off frequency control
signal to the low-pass filter (IC5) for
CTCSS/DTCS switch.
74 XCTS
Input port for the connected modem
unit via external connector (J9).
75 XRTS
Output port for the connected modem
unit via external connector (J9).

Icom IC-F521 Specifications

General

Brand	Icom
Model	IC-F521
Category	Transceiver
Language	English