12.7 Monitoring The Ft Output Of The Commreq Function Block; 12.8 Monitoring The Commreq Status Word - GE RX3i User Manual

12.7 Monitoring the FT Output of the COMMREQ Function Block.

The COMMREQ function block indicates its status through its FT output:
If after executing a COMMREQ Function, the FT Output is ON, 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. This value should always be 65536 decimal (10000H) for the CPU Ethernet daughterboard,
or 0 decimal (0000H) for the Ethernet module.
▪
Invalid Data Block length (0 or greater than 128).
This output also may indicate that no more COMMREQ functions can be initiated in the ladder program until the
Ethernet Interface has time to process some of the pending COMMREQ functions.
If the FT Output is set, the CPU did not transfer the Command Block to the Ethernet Interface. In this case, the
other status indicators are not updated for this COMMREQ. The Ethernet Interface is unable to return a
COMMREQ Status Word to the PLC logic application.

12.8 Monitoring the COMMREQ Status Word

Every COMMREQ Command Block instruction specifies a 1-word memory address to receive status information
about the execution of the command.
Before executing a COMMREQ for the Ethernet interface, the application program logic should the associated
status word zero (for example, using a MOVE Word instruction). After executing a COMMREQ, the program
should monitor its status word. If the status word is updated to a one (1), the command has been processed
successfully. If the status word is updated to a value other than 1, an error has occurred. Any data returned by
that command should not be used until the problem is corrected and the status word indicates success. It is
critical to monitor the COMMREQ status word for each COMMREQ function. .
If after executing a COMMREQ function, the COMMREQ status word is zero (0), the success Output is ON and the
FT Output is OFF, the Command Block has been sent to the Ethernet Interface, but no status has been returned.
If this condition persists, check the Controller Fault Table for information.
GFK-2224Q
(Enable ) -------------
(Command Block address) -
(Rack/Slot Location of
-
the Ethernet Interface)
(Task value) -
Figure 90: Monitoring FT Output in COMMREQ Function Block
COMM
- CommReq Delivered
REQ
FT
IN - Function Faulted (logic)
SYSID
TASK
January 2017
Chapter 12. Diagnostics
219