Indoor / Outdoor Interface Circuit 5 - 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
C804
0V
C821 R821
I/F 0V
C822
D101
Terminal board
C
D
D C
Terminal board
Interface
relay
12V
0V
L811
HIC
5V 5V
Q803
R810
10
R811
0V
5V 5V
11
0V 0V
0V
Indoor P.W.B.
Outdoor P.W.B.
35V
0V
5V
L801
R801
R802 Q801
C801
C804
C802
C803
NF COIL
C805
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 5
5V
0V
0V
5V
5V
0V 0V
5V
Q201
D210
R803
0V 0V
5V 5V 5V
R252 R249
R253
R251
C236
R250
0V
0V
0V
– 59 –
Indoor 5
IF transmit
output (SDO)
0V
IF receive
input (SDI)
0V
5V
R245
R244
R248
R247
Q215
R246
D215
0V
0V
C234
0V
Micro
computer
16 SDO1
SDI1
77