Mitsubishi Electric MELSEC Q Series Programming Manual page 98

3 START-UP PROCEDURES
(4) PLC system setting
Check that the value of High speed set in Timer limit setting is "10.00" (default
value).
P0 to P19 are used as local pointers in the safety observation sequence program.
Use P20 or later as common pointers. If a common pointer No. is set to be a
smaller number than P20, the "self-diagnostic error (error code: 4021) occurs in
the PLC CPU, the PLC CPU will stop when the pointer is used.
POINT
Do not change the value of High speed set in Timer limit setting from "10.00".
"Safety observation error (error code: 34)" will occur at the system's power supply
ON or after 24-hour continuous operation.
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