GE GFK-1541B manual Description of the Status Data, FT Output of the Commreq Function Block

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The COMMREQ Status word (CRS word) is returned from the Ethernet Interface to the PLC CPU immediately if the Command Block contains a syntax error or if the command is local. For remote commands with no syntax error, it is returned either after the channel is established successfully and the first transfer has completed or if there is an error establishing the channel. The location of the CRS word is defined in the Command Block for the COMMREQ function.

The Detailed Channel Status words (DCS words) are returned from the Ethernet Interface to the CPU only by executing the Retrieve Detailed Channel Status Command. If a channel error is indicated (by the Channel Error bit) after the channel is established, the first word of the DCS words will contain an error code indicating the cause of the error. The second word of the DCS words indicates whether the channel is active or idle.

Be aware that the Detailed Channel Status words are updated every time the status of the channel changes. If, for example, the channel is operating with a fast repetition period, the status words may change faster than the ladder executes the COMMREQ to retrieve them. Therefore, some status values may be missed from the ladder’s point of view.

Description of the Status Data

The errors and status reported in each type of status data are described below.

OK Output of the COMMREQ Function Block (Series 90-70 PLCs Only)

The OK output is set if the PLC CPU has successfully delivered the COMMREQ to the Ethernet Interface.

FT Output of the COMMREQ Function Block

The FT Output passes power upon the following errors:

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

ƒInvalid Task ID.

ƒInvalid Data Block length (zero or greater than 128).

ƒToo many simultaneous active COMMREQs (overloading either the PLC CPU or the Ethernet Interface).

3-32 TCP/IP Ethernet Communications for the Series 90™ PLC User's Manual– May 2002 GFK-1541B