GE GFK-1004B user manual Types of Status Data

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Section 4: Status Data

This section describes all the status data that is available to the ladder program to deter- mine the state of the Ethernet Interface and its channels.

Types of Status Data

There are four main types of status data available to your ladder program.

1.OK Output of the COMMREQ Function Block. This output is set if the PLC CPU was successful in transferring the COMMREQ data from the reference table memory specified by the COMMREQ function block into the memory local to the Ethernet Interface. This does not indicate that the Ethernet Interface has processed the COMMREQ, only that it has been received by the Ethernet Interface.

Barring ladder programming errors, the OK and FT outputs should not both be set in the same scan by the same COMMREQ.

2.FT Output of the COMMREQ Function Block. This output is set if there is a programming error in the COMMREQ Function Block itself, if the rack and slot specified in the COMMREQ Task parameter is not configured by Logicmaster 90-70 to contain an Ethernet Interface, or if the data block length specified in the Command Block is out of range. 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 does not transfer the Command Block to the Ethernet Interface. In this case, the other status indicators are not updated for this

COMMREQ.

3.Status Bits. The status bits are updated in the CPU once each PLC scan by the Ethernet Interface. These bits are generally used to prevent initiation of a COMMREQ function when certain errors occur or to signal a problem on an established channel. The status bits include the LAN Interface Status bits and the Channel Status bits. The starting location of these bits is user-configurable. See Chapter 2 for more information.

The LAN Interface Status bits monitor the health of the Ethernet Interface itself such as the LAN Interface OK bit and the AUI Fuse Blown bit. The Channel Status bits monitor the health and progress of a channel established using the Establish Read/ Write Channel Commands.

4.Communications Status Words. There are two types of words that provide detailed information: The COMMREQ Status word (CRS word) and the Detailed Channel Status words (DCS words). The communications status words are not updated in the CPU each scan as are the status bits. They are generally used to determine the cause of a communications error after the COMMREQ function is initiated. The cause is reported in the form of an error code described later in this section.

GFK-1004B Chapter 4 Programming Communications Requests 4-25