Format Of The Communication Request Function; Parameters Of The Commreq Function - GE VersaMax PLC User Manual

12.1 Format of the Communication Request Function

Input/ Output
enable
IN
SYSID
TASK
FT
226 GFK-1503E
For public disclosure
Serial I/O is implemented through the use of Communication Request (COMMREQ)
functions. The operations of the protocol, such as transmitting a character through the
serial port or waiting for an input character, are implemented through the COMMREQ
function block. In CPUE05, Serial I/O is not available for Port 1 when that port is
configured or forced for Station Manager operation.
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.
First word of command block
Location
Task identifier

12.1.1 Parameters of the COMMREQ Function

Choices
When the function is energized, the
flow
communications request is performed.
R, AI, AQ
IN contains the first word of the command block.
SYSID contains the rack number (most
significant byte) and slot number (least
I, Q, M, T, G, R, AI, AQ,
significant byte) of the target device. For the
constant
CPU, SYSID must specify rack/slot 0.
TASK specifies the port for which the operation is
intended:
R AI, AQ, constant
FT is energized if an error is detected processing
the COMMREQ:
(SYSID).
flow, none
(TASK).
command block) does not exist.
COMM_
Enable
REQ
FT
IN
SYSID
TASK
Description
task 19 for port 1
task 20 for port 2
•The specified target address is not present
• The specified task is not valid for the device
• The data length is 0.
• The device's status pointer address (in the
VersaMax PLC User Manual