IDEC MICROSmart FC6A Series User Manual page 631

Troubleshooting Diagram 14
Modbus RTU master
communication does not work.
Are communication
parameters equal at master and
slave?
YES
When the communication
error status is configured, is the error
information stored?
NO
Set to use a request
YES
execution device and the device
is not turned on.
NO
Make sure that slave address settings are
correct.
Turn on the request execution device.
*1 See Chapter 6 "Modbus RTU Master Communication" - "Communication Completion and Communication Error" in the "FC6A Series MICROSmart
Communication Manual".
NO
Confirm communication settings using
WindLDR.
YES
*1
Confirm the slave number (high-order
byte) and error code (low-order byte)
See the request table to find which request
has an error and what error occurred.
Confirm slave settings again.
FC6A S MICROS
ERIES
Is it clear which
request has an error?
NO
01h (function error)?
NO
02h (access destination error)?
NO
03h (device
quantity error, 1-bit write
data error)?
NO
16h (timeout error)?
NO
U ' M FC9Y-B1722
MART SER S ANUAL
13: T
*1
.
YES
YES
Make sure that the slave is compatible
with the function code.
YES
Make sure of the valid slave address
range and master settings.
Data size and actual data may not
YES
match. Make sure that slave settings
and hardware are correct (without noise
and failure).
YES
Make sure that the slave number and
communication settings are correct.
ROUBLESHOOTING
13-23