Panasonic FP-E Programming Manual page 1041

Precautions during programming
The internal relay R9009 (carry flag) used for detection of data changes is updated at each execution of the
instruction.
For this reason,
Programs using R9009 should insert it immediately after an F373 (DTR)/P373 (PDTR) instruction.
Output to an output relay or internal relay to hold the result. (Refer to the explanation of F64 (BCMP)/P64
(PBCMP).)
As in the program example on preceding page, be sure to add the trigger (X10) for the F373 (DTR)/P373
(PDTR) instruction before the internal relay R9009 (carry flag).
If the always on relay (R9010) is the execution condition, this trigger (X10) is not necessary.
Flag conditions
・Error flag (R9007):
・Error flag (R9008):
・Carry flag (R9009): Turns on if a change has occurred in the specified data area.
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Turns on and stays on when the area specified using the index modifier
exceeds the limit.
Turns on for an instant when the area specified using the index modifier
exceeds the limit.
High−level Instructions
3 − 777