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MELSEC-Q
APPENDICES
Appendix 5 Special Register (SD) for Remote I/O Module
The special register (SD) is an internal register whose application is fixed in the
programmable controller. For this reason, the special register cannot be used in the
same way as other internal registers used in sequence programs. However, data can
be written to the special register to control the CPU module or the remote I/O module
as needed.
Data is stored in binary format if not specified.
To monitor and write data to the special register of the remote I/O module, use GX
Developer or the READ/WRITE instructions in the sequence program.
Connect GX Developer to the remote master station or remote I/O station to perform
monitoring and device tests. With the sequence program, execute the READ
instruction to read data from the special register and execute the WRITE instruction to
write data to the special register.
The list in this section provides only the special register areas related to the remote I/O
module. The following table shows how to read the special register list.
Item Description
Number
• Indicates special register number
Name
• Indicates name of special register
Meaning
• Indicates contents of special register
Explanation
• Discusses contents of special register in more detail
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 (sequence programs or test operations from peripheral devices)
S/U
: Set by both system and user
<When set>
Indicated only for registers set 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 occurs
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 corresponding special register in ACPU (D9
)( 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 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 QCPU
QnU : Can be applied to Universal model QCPU
QnA: Can be applied to QnA series and Q2ASCPU series
Rem: 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) of 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)