Hitachi RAF-50FX8 Service Manual page 92

Fig. 2-1 shows the interface circuit used for the indoor and outdoor microcomputers to communicate with each other.
5V
R813
C802 R812
Q803
C805
C803
C804
5V
0V
0V
C821 R821
I/F 0V
C822
D101
0V
Terminal board
D C
C
D
Terminal board
35V
0V
C809
12V
interface
relay
0V
C811 C807
C808 NF COIL2
C812
L802
5V
5V
R807
R805
IC801
7
R810
R811
R806
Q802
5V 5V
5V
R822
R826
R824
D821
3
1
2
R823
IC801
R825
C823
0V
0V 0V
Indoor P.W.B.
Outdoor P.W.B.
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
R803
5
6
R804
C801
Q801
0V
0V
0V
5V
R829
R827
R830
Q821
C824
R828
0V
0V
0V
5V
30
R803
0V
0V
5V
5V 5V
29
0V 0V 0V
– 112 –
IF transmit
50
output(TXD2)
Microcomputer
IF receive
49
input(RXD2)
HIC
5V
0V
0V
0V
0V
11
IF transmit
output(SDO)
Micro
computer
AX-8T11
IF receive
69
input(SDI)