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User Manual
GFK-1503F
The COMMREQ requires that all its command data be placed in the correct order (in a
command block) in the CPU memory before it is executed. The COMMREQ should then be
executed by a contact of a one-shot coil to prevent sending the data multiple times. A series
of Block Move (BLKMV) commands should be used to move the words to create a command
block in the Register tables.
The COMMREQ function has three inputs and one output. When the function receives
power flow, a command block of data is sent to the specified module
Figure 200
12.1.1
Parameters of the COMMREQ Function
Input/
Output
enable
IN
SYSID
TASK
FT
Serial I/O / SNP / RTU Protocols
Choices
Description
flow
When the function is energized, the communications request is
performed.
R, AI, AQ
IN contains the first word of the command block.
I, Q, M, T, G, R,
SYSID contains the rack number (most significant byte) and slot
AI, AQ,
number (least significant byte) of the target device. For the CPU,
constant
SYSID must specify rack/slot 0.
R AI, AQ,
TASK specifies the port for which the operation is intended:
constant
task 19 for port 1 task 20 for port 2
flow, none
FT is energized if an error is detected processing the COMMREQ:
•
The specified target address is not present (SYSID).
•
The specified task is not valid for the device (TASK).
•
The data length is 0.
•
The device's status pointer address (in the command block)
does not exist.
Chapter 12
Jan 2020
202
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