GE GFK-1004B user manual Status Data

4

Status Data

There are several types of status available to the client PLC logic program.

LAN Interface Status Bits (LIS Bits): The LIS bits comprise bits 1-16 of an 80-bit status area.* The location of this 80-bit status area is assigned using the Logicmaster 90 Configuration Package in the ªStatus Addressº field. The LIS bits contain information on the status of the Local Area Network (LAN) and the Ethernet Interface itself. See Section 4 for more information.

Channel Status Bits: The Channel Status bits comprise bits 17-80 (64-bits) of the status indication area. The first 32 bits consist of an error bit and a data transfer bit for each of the 16 channels that can be established. The last 32 bits are reserved for future use and set to zero by the Ethernet Interface. See Section 4 for more information.

COMMREQ Status Word (CRS Word): The 16-bit CRS word will receive the initial status of the communication request. The location of the CRS word is assigned for each COMMREQ function in the COMMREQ Command Block. See Section 4 for more information.

Detailed Channel Status Words (DCS Words): This detailed status data is retrieved for a particular channel using the Retrieve Detailed Channel Status Command. See Section 3 for information on the command and Section 4 for the contents and format of the retrieved channel status.

FT Output of the COMMREQ Function Block: This output indicates that the PLC CPU detected errors in the COMMREQ Function Block and/or Command Block and did not pass the Command Block to the Ethernet Interface. See Section 4 for details.

The Logic Program Controlling Execution of the COMMREQ FunctionBlock

Care must be taken in developing the logic that controls the execution of the COMMREQ function. The COMMREQ function must be initiated by a one-shot to prevent the COMMREQ from being executed repeatedly each CPU scan, as this will overrun the capability of the Ethernet Interface and possibly require a manual restart. Checking certain status bits before initiating a COMMREQ function is also important. In particular, the LAN Interface OK bit should be used as an interlock to prevent execution of the COMMREQ function when the Ethernet Interface is not operational.

See Section 5 and Appendix D for tips on developing your program.

*This Section assumes you have configured your Ethernet Interface in TCP/IP con- figuration mode rather than MMS-ETHERNET configuration mode. MMS-ETHER- NET configuration mode provides only 16 bits of LIS.

4-4 TCP/IP Ethernet Communications User's Manual ± January 1996 GFK-1004B