Mitsubishi MELSEC-A series, Programming Manual

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APP - 13
APPENDICES
Appendix 1.2 Special Relays for Link
The link special relays are internal relays which are switched on/off by various factors
occurring during data link operation.
Their ON/OFF status will change if an error occurs during normal operation.
These special registers are applicable to all types of CPUs except the A3V.
For description of the special registers for link for the A3V, refer to the A3VTS Data Link
System User’s Manual.
(1) Link special relays only valid when the host is the master station
Table 1.2 Link Special Relay List
Number Name Description Details
M9200
LRDP instruction
received OFF:Unreceived
ON: Received
• Depends on whether or not the LRDP (word device read)
instruction has been received.
• Used in the program as an interlock for the LRDP
instruction.
• Use the RST instruction to reset.
M9201
LRDP instruction
complete OFF:Incomplete
ON: Complete
• Depends on whether or not the LRDP (word device read)
instruction execution is complete.
• Used as a condition contact for resetting M9200 and
M9201 after the LRDP instruction is complete.
• Use the RST instruction to reset.
M9202
LWTP instruction
received OFF:Unreceived
ON: Received
• Depends on whether or not the LWTP (word device write)
instruction has been received.
• Used in the program as an interlock for the LWTP
nstruction.
• Use the RST instruction to reset.
M9203
LWTP instruction
complete OFF:Incomplete
ON: Complete
• Depends on whether or not the LWTP (word device write)
instruction execution is complete.
• Used as a condition contact to reset M9202 and M9203
after the LWTP instruction is complete.
• Use the RST instruction to reset.
M9206
Link parameter error
in the host OFF:Normal
ON: Error Depends on whether or not the link parameter setting of the
host is valid.
M9207
Link parameter
unmatched between
master station
OFF:Normal
ON: Unmatched
Depends on whether or not the link parameter setting of the
master station in tier two matches that of the master station
in tier three in a three-tier system.
(Valid only for the master stations in a three-tier system.)
M9210
Link card error
(master station) OFF:Normal
ON: Error Depends on presence or absence of the link card hardware
error. Judged by the CPU.
M9224 Link status
OFF:Online
ON: Offline, station-to-station
test, or self-loopback test
Depends on whether the master station is online or offline or
is in station-to-station test or self-loopback test mode.
M9225 Forward loop error
OFF:Normal
ON: Error
Depends on the error condition of the forward loop line.
M9226 Reverse loop error
OFF:Normal
ON: Error
Depends on the error condition of the reverse loop line.
M9227 Loop test status
OFF:Unexecuted
ON: Forward or reverse loop
test being executed
Depends on whether or not the master station is executing a
forward or a reverse loop test.