Indoor / Outdoor Interface Circuit - Hitachi RAM-55QH5 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
C806
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
5V
0V
0V
5V
5V
0V 0V
5V
Q201
R283
D209
R803
0V 0V
5V 5V 5V
R262 R259
R263
R261
C216
R260
0V
0V 0V
– 78 –
IF transmit
output (SDO)
Micro
0V
computer
IF receive
input (SDI)
0V
IC8
15 2
5V
R255
R254
R258
R257
Q206
R256
D206
0V
0V
C214
0V
73 SDO1
SDI1
68