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Appendix 2 SPECIAL RELAY LIST
Special relays, SM, are internal relays whose applications are fixed in the Programmable
Controller.
For this reason, they cannot be used by sequence programs in the same way as the
normal internal relays.
However, they can be turned ON or OFF as needed in order to control the CPU module
and remote I/O modules.
The heading descriptions in the following special relay lists are shown in TableApp.2.1.
Item
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
• 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 GX Developer)
S/U
: Set by both system and user
<When set>
Set by
Indicated only for registers set by system
(When set)
Every END
Initial
Status change
Error
Instruction execution : Set when instruction is executed
Request
For details on the following items, refer to the following manuals:
• Networks
TableApp.2.1 Descriptions of the special relay lists headings
: Set during every END processing
: Set only during initial processing (when power supply is turned ON, or when going from STOP to RUN)
: Set only when there is a change in status
: Set when error occurs
: Set only when there is a user request (through SM, etc.)
Manuals of each network module
In the program that achieves the safety function, only SM1000 to SM1299 can be
used.
Special relay other than SM1000 to SM1299 cannot be used in the program that
achieves the safety function.
Function of Item
Appendix 2 SPECIAL RELAY LIST
App-11
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