V
BN
V
HL
Control is performed by exchanging signals between outdoor unit, indoor unit and remote controller by M-NET
transmission. If noise should enter into the transmission line, the normal transmission will be hindered causing
erroneous operation.
(1) Symptom caused by the noise entered into transmission line
52
µ
s
52
µ
s
52
µ
s
52
µ
s
52
µ
s
(2) Method to confirm wave shape
No fine noise allowed
No fine noise
allowed
Logic value
Transmission line voltage level
0
V
HL
= 2.0V or more
1
V
BN
= 1.3V or less
[With transmission]
[Without transmission]
Logical value
Logica valuel
“0”
“1”
Noise entered into
transmission line
Signal changes and is misjudged as the signal of other address.
6600
Transmission wave shape changes to other signal due to noise.
6602
Transmission wave shape changes due to noise, and can not be received
6607
normally thus providing no reply (ACK).
Transmission can not be made continuously due to the entry of fine noise.
6603
Transmission can be made normally, but reply (ACK) or answer can not be
6607
issued normally due to noise.
6608
Cause
Erroneous operation
Error code
❉
1
❉
1
Check the wave shape of transmission line with an oscilloscope to confirm that the following conditions are being
satisfied.
1) The figure should be 104
µ
s/bit
±
1%.
2) No finer wave shape (noise) than the transmission signal (52
µ
s
±
1%) should be allowed.
❉
1
3) The sectional voltage level of transmission signal should be as follows.
❉
1 However, minute noise from the DC-DC converter or inverter operation may be picked up.
- 131 -
[3] Investigation of Transmission Wave Shape/Noise
1. M-NET transmission