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11. Indoor/outdoor communication circuits
Indoor transmission circuit
Indoor microcomputer (IC601)
Indoor/outdoor communication
chopper output (30kHz)
Indoor transmission output
Indoor reception input
Indoor unit reception circuit
< Typical communication waveform >
Microcomputer
transmission signal
Microcomputer
reception signal
Signal between F cables 1 and 2
Microcomputer
transmission signal
Microcomputer
reception signal
< Enlarged waveform >
Signal sent by indoor microcomputer
5ms.／DIV
・
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.)
Check
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.)
Check
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 unit side
C302
0V
The unit is receiving a signal that it sent
(it is not used particularly as a signal).
Approx.
200 ms.
Signal sent by outdoor microcomputer
30 kHz demodulated waveform
5ms.／DIV
Outdoor unit side
1
1
2
2
3
3
Fig. 11-1
Approx.
200 ms.
Signal between F cables
30 kHz demodulated waveform
5ms.／DIV
Fig. 11-2
- 58 -
Inverter circuit
Outdoor
reception
circuit
Outdoor
transmission
circuit
Signals sent by indoor and outdoor
microcomputers
1
and
2
5ms.／DIV
Outdoor
microcomputer
Outdoor
reception
input
Outdoor
transmission
output
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