GE GFK-1004B Commreq Function Block and Command Block, Commreq FunctionBlock, Rack Slot

4

Section 2: The COMMREQ Function Block and Command Block

This section describes the programming structures common to all Communications Requests: the COMMREQ Function Block and the Command Block.

The COMMREQ FunctionBlock

The Communications Request is triggered when the logic program passes power to the COMMREQ Function Block. For the Series 90-70 PLC, the COMMREQ Function Block has four inputs and two outputs:

(Enable ) ±±±±±±±±±±±±±±

(Command Block Pointer) ±

(Rack/SlotLocationof	±
the Ethernet Interface)
(Alwayszero)	00000000 ±

COMM

REQ

IN FT

SYSID

TASK

±OK

±Function Faulted(logic)

Each of the inputs and the output are discussed in detail below. It is important to under- stand that the Command Block pointer points to the location in memory you are using for the Command Block.

Enable: Control logic for activating the COMMREQ Function Block. See Section 5 and Appendix D for tips on developing your program.

IN: The location of the Command Block. It may be any valid address within a word-ori- ented area of memory (%R, %AI, %AQ, %P, or %L).

SYSID: A hexadecimal value that gives the rack (high byte) and slot (low byte) location of the Ethernet Interface.

Examples:

Rack	Slot	Hex Word Value
0	4	0004h
3	4	0304h
2	9	0209h
4	2	0402h

Note

This Series 90-70 Ethernet Interface is only supported in the main PLC rack (rack number 0).

4-6 TCP/IP Ethernet Communications User's Manual ± January 1996 GFK-1004B