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4-6 TCP/IP Ethernet Communications User’s Manual – January 1996
GFK-1004B
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 Function Block
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 ) ––––––––––––––
COMM
REQ
(Command Block Pointer)
(Rack/Slot Location of
the Ethernet Interface)
(Always zero)
00000000
–
–
–
IN FT
SYSID
TASK
– Function Faulted (logic)
– OK
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).