5-4
5
TABLE 5-2 TROUBLESHOOTING GUIDE (CONT.)
Possible
Symptom
Fault
Action or Check
No Modbus
Device Address
Check C setting and device
communication
address setting.
Wrong serial settings Check 8099 settings against
modbus device settings.
Wrong signal
Check cable wiring against
connections
the 8099 manual.
Check 8099 internal jumper
settings for correct signals.
Missing network
Check RS-485 cable for
termination
correct network terminators.
Verify voltage on termination
resistors.
RS485 Mode Off
Verify 8099 setup. RS485
must be on for 2-wire systems.
off for 4-wire and RS-232
systems.
Modbus command
Wrong command or Recheck program.
fails
command syntax
error
Query the ESR Register to
check on the cause of the
problem.
Query the Modbus Error
register to check on the cause
of the problem
Wrong output value Check Modbus device
manual.
8099 unexpectedly
Auto-disconnect
Check 8099 settings and
drops socket
set on
turn Auto-disconnect off.
connection
