GE GFK-1541B manual Status Data

4

Status Data

This section describes all the status data that is available to the ladder program to determine the state of the Ethernet Interface and its Modbus/TCP channels.

Types of Status Data

There are three main types of status data available to your ladder program:

1.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 SYSID parameter is not configured 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.

2.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 and is set in harware config when the module is configured.

The LAN Interface Status bits monitor the health of the Ethernet Interface itself, such as the LAN Interface OK bit and the AAUI Fuse Blown bit. The Channel Status bits monitor the health of a channel.

3. Communications Status Word. The COMMREQ Status word (CRS word) provides detailed information on the status of the COMMREQ request. The communications status word is not updated in the CPU each scan as are the status bits. They are generally used to determine the cause of a communication error after the COMMREQ function is initiated.

The cause is reported in the form of an error code described later in this section.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. The location of the CRS word is defined in the Command Block for the COMMREQ function.

4-20 TCP/IP Ethernet Communications for the Series 90™ PLC User's Manual– May 2002 GFK-1541B