Troubleshooting A Ladder Program - GE RX3i User Manual

Troubleshooting a Ladder Program

There are several forms of status data that can be accessed by the application program. The use of the LAN
Interface OK bit in the LAN Interface Status Word was described in the example program. Some status data
can be used to troubleshoot a program in its developmental stage. The two primary sources of this data are
the FT Output on the COMMREQ Function Block and the COMMREQ Status word (CRS word).
FT Output is ON
If after executing a COMMREQ Function, the FT Output is ON, then there is a programming error in one or more
of the following areas.
▪
Invalid rack/slot specified. The module at this rack/slot is unable to receive a COMMREQ Command Block.
▪
Invalid Task ID. For the RX3i and Rx7i ETM001 Ethernet interfaces TASK must always be set to zero. For
PACSystems CPU embedded Ethernet interface, TASK must be set to 65536 (0x10000) to address the CPU's
Ethernet daughterboard.
▪
Invalid Data Block length (0 or greater than 128).
COMMREQ Status Word is Zero (0) and FT Output is OFF
If after executing a COMMREQ function, the CRS word is zero (0) and the FT Output is OFF, then the Command
Block has been sent to the Ethernet interface, but no status has been returned yet. If this condition persists,
check the PLC Fault Table for information.
COMMREQ Status Word is Not One (1)
If after executing a COMMREQ function, the CRS word is not one (1) indicating success, then there were:
▪
Errors in the Command Block (the Channel command code or parameters), or
▪
The command parameters were valid but there was an error in completing the request.
If the CRS word does not contain a 1 indicating success, then it contains either a 0 or a code indicating what
error occurred.
GFK-2224Q January 2017
Chapter 9. Modbus/TCP Client
169