Hitachi RAM-71QH5 Service Manual page 47

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
D2 C2
Terminal board
Interface
relay
0V
L814
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
L804
R831
R832 Q804
C831
12V
C834
C832
C833
NF COIL
C835
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 4
5V
0V
0V
5V
5V
0V 0V
5V
Q204
D210B
R833
0V 0V
5V 5V 5V
R292 R289
R293
R291
C225
R290
0V
0V 0V
– 56 –
IF transmit
output (SDO)
0V
IF receive
input (SDI)
0V
5V
R285
R284
R288
R287
Q209
D209 R278
0V
0V
C227
0V
Micro
computer
10
SDO4
SDI4
72