GE GFK-1541B Commreq Status Word is Zero 0 and FT Output is OFF, Commreq Status Word is Not One

3

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.

ƒInvalid rack/slot specified. The module at this rack/slot is unable to receive a COMMREQ Command Block.

ƒInvalid Task ID. For the Series 90-30 Ethernet Interface and the Series 90-70 Ethernet Interface (Type 2), this value should always be zero. For the Series 90-30 CPU364, this value should always be 21 decimal (0015H).

ƒInvalid 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:

ƒErrors in the Command Block (the Channel command code or parameters), or

ƒFor an establish command (Establish Read Channel, Establish Write Channel, or Send Information Report), the command parameters were valid but there was an error in establishing a channel.

If the CRS word does not contain a 1 indicating success, then it contains either a 0 or a code indicating what error occurred.

Monitoring the Communications Channel

Once you have a working ladder program, you can use the status data to monitor your communications activity and take the desired action upon certain events. The primary indicators of a communications channel are the Channel Status bits: Channel Error bit and Data Transfer bit. In addition, the CRS word and the DCS words can be used to more precisely troubleshoot any problems that may occur.

Monitoring the COMMREQ Status Word

It is critical to monitor the CRS word for each COMMREQ function you initiate. First, zero the associated CRS word before executing the COMMREQ function. Then when the CRS word becomes non-zero, you know the Ethernet Interface has updated it. If the CRS word is updated to a one (1), then the Command Block was processed successfully by the Ethernet Interface. If the CRS word is updated to a value other than 1, then an error has occurred in processing the Command Block. Do not use data received from a server until the CRS word for that channel is 1 or the Data Transfer bit goes to 1.

3-46 TCP/IP Ethernet Communications for the Series 90™ PLC User's Manual– May 2002 GFK-1541B