ICS ELECTRONICS 4809A, Instruction Manual

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5-6
5
TABLE 5-2 TROUBLESHOOTING GUIDE
CONTINUED
Possible
Symptom Fault Action or Check
No response from Wrong GPIB address Turn unit off and back on.
GPIB commands Watch LEDs to check address
setting.
ERR LED comes on Bad command Check command syntax.
Query the ESR register to
determine the cause of the
error.
Modbus Error If ESR bit 6 is on, query the
Modbus Error Register with
the E? command.
No communication Wiring error Check RS-232 or RS-485
with Modbus device cable wiring against figures
in Section 2. Modbus TXD
signal must go to 48x9A
receive input. Use an
RS-232 Tracker or DVM to
find Modbus TXD signal.
TXD will be -6 to -12 Vdc.
Parameter setting Check 4899A Serial settings
mismatch vs the settings on the Modbus
device. Use the SCPI com-
mands in Table 3-2 to query
or change the 4899A settings.
Set the serial parameters
to match. Save new 4899A
settings with the *SAV 0
command. Power cycle the
4899A or use the
SYST:COMM:SER:UP
command to activate the new
settings.