Icom IC-2GA Service Manual page 14

(9)
T5/R5
SWITCHING CIRCUIT
(MAIN
UNIT)
When
the
PTT
switch (S205)
is
pushed,
Q216
Is
turned
on.
The
collector of
Q215
outputs a
"LOW"
signal to
the
CPU
(IC503, pin
44).
Using
the
"LOW"
signal,
the
CPU
sends
TRANSMIT
data to IC202.
IC202 (pin 13)
outputs
a
"HIGH"
signal to
IC203C
(pin
8)
and IC203A
(pins 12
and
13),
controlling
IC203C
(pin 10)
—
shutting off
R+5.
Releasing the
PTT
switch turns
off
0216.
The
collector of
0215
outputs
a
"HIGH"
signal
which causes the
CPU
to
send RECEIVE
data to IC202.
IC202
(pin 13)
outputs
a
"LOW"
signal to
IC203C
(pin
8)
and IC203A
(pins
12
and
13),
controlling
IC203C
(pin 10)
—
turning
on R+5S.
IC203A
(pin 11)
outputs
a
"HIGH"
signal to
IC203B
(pin
2)
controlling
the
base
of
0209
—
turning
off
T+5.
IC203A
(pin 11)
outputs
a
"LOW"
signal to
IC203B
(pin
2),
controlling
the
base
of
0209
—
turning
on T+5.
T5/R5
SWITCHING CIRCUIT
+5S
R+5
'
H:
ON
L:
OFF
Q213,
Q214
A
B
Y
L
H
L
H
L
H
L L
H
~T~
Vcc
T+5-
10
Q211, Q212
i\a\
a (/)
11 12 13
14
IC202
SHIFT
REGISTER
5V>-^
H:
ON
L:
OFF
Q209,
Q210
12
13
-I/O
STL8
-DATA
-CK
4
-
6
CPU
(IC501)
PORT ALLOCATION
PIN
STANDBY
OPEfU^TION
ft-
....
NAME
DESCRIPTION
i
H/L
1~28 S13-S31
COM
29
P40
0
L
0
L
KSO
Output
for the
SW
matrix.
30 P41
0
L
0
L
KS1 Output
for the
SW
matrix.
31
P42
0
L
0
L
KS2 Output
for
the
SW
matrix.
32 P43
0
L
0
L
KS10
Output
for
the
SW
matrix.
33
Vss
Ground
34 P50
0
L
1
L
KRO
Input for
the matrix
return.
35 P51
0
L
1
L
KR1
Input for the matrix return.
36
P52
0
L
1
L
KR2
Input
for
the matrix
return.
37 P53
0
L
1
L
KR3
Input for the matrix
return.
38 POO
1
L
1
1
INT4
Standby
detector input.
Goes
to
standby
at
the
end
of a pulse.
39 P01
1
L
0
J CK
Serial
data output
clock:
a)
PLLN
b)
CTCSSTONE
c)
I/O
EXPANSION
40 P02
1
L
0
H
DATA
Serial data
output synchronized with CK.
41
P03
1
L
1
H
BUSY BUSY
input
used
when
a signal
is
received.
42 P10
1
L
1
L
LAM
PI Input
used
for
lamp
output
HI/LOW
control.
43 P11
1
L
1
L
MON1
.
Input
used
for
ON/OFF
control of
SQL OFF and BEEP
output.
44
PI 2
1
1
L
1
L
PTT
Tx/Rx
switching input.
45
PI 3
1
L
1
L
FUNC
Switches matrix input
to
FUNC
functions.
46 P20
0
L
0
L
KSI1 Output
for the
initial
matrix.
4-5