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W
IRING AND
I
NSTALLATION
C
OMMUNICATION
C
ONNECTIONS
MATRIX BACnet Router User Manual (6/6/2007)
2-9
2.3.2.4 LED I
NDICATION
Located below the network termination and biasing switches is a set of diagnostic LEDs that can be useful
for troubleshooting network communication problems with a MS/TP network.
Figure 2-8 Network Diagnostic LEDs
Table 2-1: EIA-485 LED Diagnostics
LED Position Notes
TXD This LED will flash anytime data is transmitted by MATRIX BACnet Router to
the MS/TP network. On an active network, this light should flash anytime the
device passes the token to another device or routes a request made by another
device on the BACnet/IP or BACnet/Ethernet network.
RXD This LED will flash anytime data is received by MATRIX BACnet Router from
the MS/TP network. On an active network, this light should flash anytime there
is activity on the MS/TP network.
PERR THis LED will flash upon the event a parity error occurs on the MS/TP network.
A parity error is caused by a mismatch between the calculated checksum and
value received with the packet. The most common reason for a packet error is if
more than one unit is attempting to communicate on the network at once,
indicating the presence of a duplicate token or duplicate MAC Address.
BERR This LED will flash upon the event a byte error occurs on the MS/TP network. A
byte error is caused when information is lost during network communications,
and is detected in the start, stop, or data bit timings. The most common reason
for a byte error is due to devices attempting to communicate on the MS/TP
network at different baud rates.
TXD
RXD
PERR
BERR