If a cable poorly inserted in the indoor terminal board or some other failure overheats the terminal board and the
temperature fuse of the terminal board blows out, the power to the indoor communication circuit will be shut down to stop
the communications function. (In that case, the failure will be displayed by the timer lamp blinking 3 times.)
If communication fails between the indoor and outdoor units for some reason, the product will give a self-diagnosis
display either by "the timer lamp blinking 3 times" or "the timer lamp blinking 12 times" depending on the cause.
Indoor and outdoor communications are conducted by using lines 2 and 3 of F cable. Line 2 of F cable is shared with a
transmission channel that powers the outdoor unit.
Data communicated between the indoor and outdoor units are outputted from the microcomputer as serial signals and are
transmitted as demodulated by a 30 kHz carrier wave. (Both the indoor and outdoor microcomputers directly output a signal
demodulated at 30 kHz.)
< Typical communication waveform >
Signal between F cables 1 and 2
< Enlarged waveform >
Fig. 11-2
Fig. 11-1
F
E
D
G
H
DSignal sent by indoor microcomputer
DIV
9
G
Signal sent by outdoor microcomputer
ˍ˲ˋ',9
9
HE
Signals sent by indoor and outdoor
microcomputers
ˍ˲ˋ',9
9
F
Signal between F cables and
5ms.DIV 5ms.DIV
ˍ˲ˋ',9
9
The unit is receiving a signal that it sent
(it is not used particularly as a signal).
F
Outdoor
reception
circuit
Outdoor
transmission
circuit
Outdoor
microcomputer
Inverter circuit
Indoor unit side Outdoor unit side
9
5
5
&
&
5
&
5 5
4
/
5
9
G
H
1 Outdoor
reception
input
26Outdoor
transmission
output
D
E
9
&
Indoor transmission circuit
Indoor unit reception circuit
Indoor/outdoor communication
chopper output (30kHz)
Indoor transmission output
Indoor reception input
Indoor microcomputer
˟
ˮ
˟
ˮ
ˮ
ˮ
ˮ
ˮ
ˮ
˭
˟
˰
˲
˲
˭
63
66
65
Indoor side
Microcomputer
transmission signal
Microcomputer
reception signal
Microcomputer
transmission signal
Microcomputer
reception signal
Outdoor side
Approx.
200 ms.
Approx.
200 ms.
Check
Check
5ms.DIV5ms.DIV
C302
0V
11. Indoor/outdoor communication circuits
3 3
1 1
2 2
30 kHz demodulated waveform
30 kHz demodulated waveform
12
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