Sending Commands from a PLC
Timing of
Communications Flag
Changes
Example
Communications Port Enabled Flag
Communications instruction:
SEND(090), RECV(098), CMND(490)
Communications Port Error Flag
Communications Port Completion Code
102
• The Communications Port Enabled Flag remains OFF during communica-
tions and turns ON when they are completed (regardless of whether or
not an error occurs).
• The Communications Port Error Flag retains its status until the next trans-
mission or reception.
• The Communications Port Error Flag turns OFF with the execution of the
next communications instruction even if there was an abnormal comple-
tion.
Instruction 1
being executed.
Completion
0000 (Normal completion)
Instruction 2
Instruction 3
being executed.
being executed.
0000 (Normal completion)
(Unit address setting error)
Section 7-2