Mitsubishi Electric PURY-EP200YLM-A, Service Handbook, Page: 321 / 434

[8-4 Checking Transmission Waveform and for Electrical Noise Interference ]
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HWE1314A GB
8-4 Checking Transmission Waveform and for Electrical Noise
Interference
8-4-1 M-NET
Control is performed by exchanging signals between the outdoor unit and the indoor unit (ME remote controller) through M-
NET transmission. Noise interference on the transmission line will interrupt the normal transmission, leading to erroneous op-
eration.
(1) Symptoms caused by noise interference on the transmission line
(2) Wave shape check
Wave shape check
Check the wave pattern of the transmission line with an oscilloscope. The following conditions must be met.
1) Small wave pattern (noise) must not exist on the transmission signal. (Minute noise (approximately 1V) can be generated by
DC-DC converter or the inverter operation; however, such noise is not a problem when the shield of the transmission line is
grounded.)
2) The sectional voltage level of transmission signal should be as follows.
Cause Erroneous operation Error code Error code definition
Noise interference on
the transmission line
Signal is transformed and will be misjudged as the
signal of another address.
6600 Address overlap
Transmission wave pattern is transformed due to
the noise creating a new signal
6602 Transmission pro-
cessor hardware er-
ror
Transmission wave pattern is transformed due to
the noise, and will not be received normally leading
to no acknowledgement (ACK).
6607 No ACK error
Transmission cannot be performed due to the fine
noise.
6603 Transmission line
bus busy error
Transmission is successful; however, the acknowl-
edgement (ACK) or the response cannot be re-
ceived normally due to the noise.
6607
6608
No ACK error
No response error
Logic Voltage level of the transmission line
0 V
HL
= 2.5V or higher
1 V
BN
= 1.3V or below
[With transmission]
[Without transmission]
No fine noise allowed
No fine noise
allowed
52 52 52 52 52
V
BN
V
HL
Logic "0" Logic "1"