GE 90-30 PLC Switch User Manual

TCP/IP Ethernet Communications User’s Manual - August 1997 GFK-1084B
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 or CIMPLICITY Control in the “Status Address” 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
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
Function Block
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.