BAS-SVX51L-EN 42
Troubleshooting Options
Plug comm link into IMC
Min = 0.59
Max = 0.61
Avg = 0.59
(voltage range is very flat)
Tx = off
Rx = solid on
Junk during idle only. No other diagnostics
Duplicate rotary switch address
Normal
Min = 0.33
Max = 0.60
Avg = 0.45
(refer to Note
(b)
)
Units with duplicate addresses have a
normal interval then:
Tx = off
Rx = flashing for several seconds,
other units are normal
Junk during idle — framing errors
Bad Header
Retry of token from X > Z
X is the duplicate address
(refer to sample capture)
Mixed baud rate
Normal
Min = 0.33
Max =0.60
Avg = 0.45
(refer to Note
(b)
)
Dominant speed units normal
Tx = quick flash
Rx = almost solid on
Quiet units
Tx = off
Rx = almost solid on
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.
(c)
However,
devices communicating at a different baud
rate will be silent—no Tx.
Power polarity reversed on shared transformer
Min = 0.10
Max = 0.20
Avg = 0.13
(very low reading with an
occasional spike to 0.60)
(refer to Note
(b)
)
Tx = inconsistent, sometimes normal
flash, sometime off
Rx = almost solid on
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.
(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.
Table 8. Characteristics associated with specific problems on the BACnet
®
MS/TP link (continued)
Condition Vdc LEDs Serial Spy
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