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MELSEC-Q
APPENDICES
Appendix 4 Special Relay (SM) for Remote I/O Stations
The special relay (SM) is an internal relay whose specification is fixed in the
programmable controller. For this reason, the special relay cannot be used in the same
way as other internal relays used in sequence programs. However, the bit of the
special relay can be turned ON or OFF as needed to control the CPU module or the
remote I/O module.
To monitor and turn ON or OFF the bit of the special relay of the remote I/O module,
use GX Developer. Connect GX Developer to the remote master station or the remote
I/O station to perform monitoring and device tests.
The list in this section provides only the special relay areas related to the remote I/O
module. The following table shows how to read the special relay list.
Item Description
Number
• Indicates the number of the special relay.
Name
• Indicates the name of the special relay.
Meaning
• Indicates the nature of the special relay.
Explanation
• Contains detailed information about the nature of the special relay.
Set by (When set)
• Indicates whether the relay is set by the system or user, and, if it is set by the system, when
setting is performed.
<Set by>
S : Set by system
U : Set by user (in sequence program or test operation at a peripheral device)
S/U
: Set by both system and user
<When set>
indicated only if setting is done by system.
Each END
: Set during each END processing
Initial
: Set only during initial processing
(when power supply is turned ON, or when going from STOP to
RUN)
Status change
: Set only when there is a change in status
Error
: Set when error is generated
Instruction execution : Set when instruction is executed
Request
: Set only when there is a user request
(through SM, etc.)
System switch : Set when the system is switched
Corresponding ACPU
M9
• Indicates special relay M9
/ corresponding to the ACPU.
(Indicates M9
format change when there has been a change in contents. Basic
model QCPU and Redundant CPU are not supported.)
• Items indicated as "New" have been newly added for Q/QnACPU
Applicable CPU
• Indicates the applicable CPU module.
: Can be applied to all types of QCPU and QnACPU
QCPU: Can be applied to all Q-series CPU
Q00J/Q00/Q01: Can be applied to Basic model QCPU
Qn(H) : Can be applied to High Performance model QCPU
QnPH : Can be applied to Process CPU
QnPRH : Can be applied to Redundant CPU
QnU : Can be applied to Universal model Q CPU
QnA: Can be applied to QnA series and Q2ASCPU series
Remote: Can be applied to the MELSECNET/H remote I/O modules.
Each CPU module type name: Can be applied only to the specific CPU module. (e.g.
Q4ARCPU, Q3ACPU)
For details on the following items, refer to the following.
• CPU
• User's Manual (Function Explanation, Program Fundamentals) for the CPU
module used
• Networks
• Q corresponding MELSECNET/H Network System Reference Manual (PLC to
PLC network)
• Q corresponding MELSECNET/H Network System Reference Manual (Remote
I/O network)
• For QnA/Q4AR MELSECNET/10 Network System Reference Manual
• SFC
• MELSEC-Q/L/QnA Programming Manual (SFC)