Hitachi RAS-50WX8 Service Manual page 73

Fig. 2-1 shows the interface circuit used for the indoor and outdoor microcomputers to communicate with each other.
Control P.W.B.
Terminal board
Terminal board
C
D
D C
Terminal board
35V
C809
interface 12V
relay
0V
C807
C811
C812 C808 NF COIL2
L802
Indoor P.W.B.
Outdoor P.W.B.
0V
5V
C801 Q801
R802
0V
0V
C802
C803
C810
C806
C804
I/F 0V
(Communications from outdoor microcomputer to indoor microcomputer)
(Communications from indoor microcomputer to outdoor microcomputer)
Fig. 2-1 Indoor/outdoor interface Circuit
5V
30
R803
0V
0V
5V
5V 5V
29
0V 0V 0V
– 112 –
I / F Reception
Microcomputer
I / F Transmission
HIC
5V
0V
0V
0V
0V
11
IF transmit
output(SDO)
Micro
computer
AX-8T11
IF receive
69
input(SDI)