Indoor / Outdoor Interface Circuit 1 - Hitachi RAM-90QH5 Service Manual

Fig. 2-1 shows the interface circuit used for the indoor and outdoor microcomputers to communicate with
G
each other.
5V
R813
R812
C802
Q803
C804
0V
0V
C821 R821
11
I/F 0V
C822
D101
0V
Terminal board
C
D
D C
Terminal board
35V
Interface
relay
12V
0V
C804
C805
L811
HIC
5V 5V
R810
10
R811
5V 5V 5V
0V
0V
Indoor P.W.B.
Outdoor P.W.B.
0V
L801
+5V
C811
0V
+5V
C812
R263
C803 0V
NF COIL
I/F 0V
(Communications from indoor micro computer to outdoor micro computer)
(Communications from outdoor micro computer to indoor micro computer)
Fig. 2-1 Indoor / Outdoor interface Circuit 1
5V
0V
0V
0V
5V
0V 0V
+5V
Q202
0V
R812
Q802
D211
0V 0V
+5V
+5V
+5V
D206
R257
IC6
0V
0V
0V
– 55 –
Indoor 1
IF transmit
output (SDO)
Micro
computer
IF receive
input (SDI)
0V
+5V
+5V
C316
1
1
Y0
5
+5V Y1
2 Y2
4
Y3
R254
3
Y
Q206
8
7 6
0V
0V
0V
M
17
IC15
I
X0 12
37
C
X1
14
X2
15 38
O
X3 11
X 13 N
78
A
10
9