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Table 8.
Characteristics associated with specific problems on the BACnet
Condition
Plug comm link into IMC
Duplicate rotary switch address
Mixed baud rate
Power polarity reversed on shared transformer
(a) A properly terminated and powered link typically shows voltage measurements between 0.30 and 0.60 with an average voltage of 0.45.
(b) These readings are typical for ordinary meters. Very good meters (Fluke) with Min/Max recording capability will detect very transitory spikes of much higher voltage.
(c) There may be one blue diagnostic message every 10,000 lines (12-30 in a 3-5 min capture). This would still represent a normally functioning link.
BAS-SVX51L-EN
Vdc
Min = 0.59
Tx = off
Max = 0.61
Rx = solid on
Avg = 0.59
(voltage range is very flat)
Normal
Units with duplicate addresses have a
Min = 0.33
normal interval then:
Max = 0.60
Tx = off
Avg = 0.45
Rx = flashing for several seconds,
(b)
(refer to Note
)
other units are normal
Normal
Dominant speed units normal
Min = 0.33
Tx = quick flash
Max =0.60
Rx = almost solid on
Avg = 0.45
Quiet units
(b)
(refer to Note
)
Tx = off
Rx = almost solid on
Min = 0.10
Tx = inconsistent, sometimes normal
Max = 0.20
flash, sometime off
Avg = 0.13
Rx = almost solid on
(very low reading with an
occasional spike to 0.60)
(b)
(refer to Note
)
Troubleshooting Options
®
MS/TP link (continued)
LEDs
Junk during idle only. No other diagnostics
Junk during idle — framing errors
Bad Header
Retry of token from X > Z
X is the duplicate address
(refer to sample capture)
The baud rate of the first units that power up
will dominate communication on the link.
SerialSpy shows a clean capture with no (or
few) blue diagnostics or errors.
devices communicating at a different baud
rate will be silent—no Tx.
Chaos. Sometimes you see one device or
more that is constantly polling, but never
finding another device.
It also might appear to be normal, but with all
the devices on that shared transformer down.
Serial Spy
(c)
However,
42
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