User`s manual

DSM314 COMM REQ
GFK-1742A Appendix B DSM314 Communications Request Instructions B-7
B
Section 2: The COMM REQ Ladder Instruction
This section discusses the COMM REQ instruction in general. More information is available in
the
Series 90-30/20/Micro PLC CPU Instruction Set Reference Manual
, GFK-0467L or later.
The Communications Request begins when the COMM REQ Ladder Instruction is activated. The
COMM REQ ladder instruction has four inputs and one output:
E
nable Input
--
C
ommand Block Pointer
R
ack/Slot Location
P
ort Number
?
??????
?
??????
?
??????
-
-
-
-
Fault Output
COMM_
REQ
I
N FT
S
YSID
T
ASK
Figure B-3. COMM REQ Ladder Instruction
Each of the inputs and outputs is discussed in detail below. It is important to understand that the
Command Block Pointer points to another location in memory where you must enter additional
information about the Communications Request.
Enable Input:
Must be Logic 1 to enable the COMM REQ Instruction. It is recommended that the
enabling logic be a contact from a transition (“one-shot”) coil.
IN:
The memory location of the first word of the Command Block. It can be any valid address in
word-type memory (%R, %AI, or %AQ).
SYSID:
A hexadecimal value that gives the rack and slot location of the module that the COMM
REQ is targeting. The high byte (first two digits of the hex number) contains the rack number,
and the low byte contains the slot number. The table below shows some examples of this:
SYSID Examples
Rack Slot
Hex Word Value
0 4 0004h
34
0304h
29
0209h
TASK:
The number 0 should always be entered here for a DSM module.
FT Output:
The function’s FT (fault) output can provide an output to optional logic that can verify
successful completion of the Communications Request. The FT output can have these states: