Appendix 2 List Of Special Relay Areas - Mitsubishi Electric Q26UD(E)HCPU User Manual

Appendix 2
The special relay (SM) is an internal relay whose application is fixed in the programmable controller. For this reason,
the special relay cannot be used in the same way as other internal relays are used in sequence programs. However,
the bit of the special relay can be turned on or off as needed to control the CPU module.
The following table shows how to read the special relay list.
Item
Number Special relay number
Name Special relay name
Meaning Contents of special relay
Explanation Detailed description of special relay
Set side and set timing of special relay
<Set by>
• S: Set by system
• U: Set by user (using a program, programming tool, GOT, or test operation from other external devices)
• S/U: Set by both system and user
<When Set>
The following shows the set timing when the special relay is set by system.
• Every END processing: Set during every END processing
Set by (When Set)
• Initial: Set during initial processing (after power-on or status change from STOP to RUN)
• Status change: Set when the operating status is changed
• Error: Set if an error occurs
• Instruction execution: Set when an instruction is executed
• Request: Set when requested by a user (using the special relay)
• When system is switched: Set when the system is switched (between the control system and the standby system)
• At write: Set when data are written to the CPU module by a user
• During END processing: Set during END processing
CPU module supporting the special relay
• QCPU: All the Q series CPU modules
• Q00J/Q00/Q01: Basic model QCPU
• Qn(H): High Performance model QCPU
• QnPH: Process CPU
Corresponding CPU • QnPRH: Redundant CPU
• QnU: Universal model QCPU
• QnUDV: High-speed Universal model QCPU
• Q00UJ/Q00U/Q01U: Q00UJCPU, Q00UCPU, and Q01UCPU
• LCPU: All the L series CPU modules
• CPU module model: Only the specified model (Example: Q02UCPU, L26CPU-BT)
Corresponding • Special relay (M9) supported by the ACPU ("M9 format change" indicates the one whose application has been changed.
ACPU Incompatible with the Q00J/Q00/Q01 and QnPRH.)
M9 • "New" indicates the one added for the QCPU or LCPU.
For details on the following items, refer to the following.
• For network related items:  Manuals for each network module
• For SFC programs:  MELSEC-Q/L/QnA Programming Manual (SFC)
Do not change the values of special relay set by system using a program or by test operation. Doing so may result in system
down or communication failure.
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List of Special Relay Areas
Description