Mitsubishi MELSEC-A Series Reference Manual page 295

9. PROGRAMMING
(5)
(6)
(7)
Write an error detection circuit in a sequence program to check the operation from
error occurrence to initial communication completion when an error occurs to a local
or remote I/O station.
(a) Whether an error has occurred in a local or remote I/O station or not can be
determined by 1/0 of bit corresponding to the specified station of D9228 to
D9231. (When the bit corresponding to the specified station is "1", it means that
an error occurs.)
(b) Whether the initial communication is being executed or not can be determined
by 1/0 of bit corresponding to the specified station of D9224 to D9227. (When the
bit corresponding to the specified station is "1", it means that initial
communication is being executed.)
(c) The occurrence of an error and the execution of initial communication in a local
station or a remote I/O station are detected in the following timing.
(d) The error detection program must be written before the initial communication
detection program.
If initial communication detection program is written first, the occurrence of errors
and the execution of initial communication may not be detected.
When RFRP and RTOP instructions cannot be executed because the special
function module is faulty, X
(a) When YnD is turned ON, X
(b) If X D is turned ON, a special function module might be faulty or the module
(n+1)
might not be mounted correctly. Check the special function module at which the
error occurred.
Write the following timing circuit to turn YnD ON/OFF with SET/RST instruction.
(a) Turn YnD ON, when X
(b) Turn YnD OFF only once, when X
D is turned ON.
(n+1)
D is turned OFF.
(n+1)
D is turned ON.
(n+1)
D is turned OFF.
(n+1)
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