High−level Instructions
3 − 60
Description
The 16-bit equivalent constant or 16-bit area specified by S and the 16-bit area specified by D are added
together.
Augend data
Trigger turns on
Result
(D) (D)+ (S)
Addend data
Precautions during programming
If the result of an arithmetic operation instruction does not fall within the range of values which can be
handled, an overflow or underflow will result.
Under normal circumstances, do not allow an overflow or underflow to occur.
If the calculated result accidentally overflows or underflows, use of the F21 (D+) instruction (32-bit data
addition) is recommended.
When you use the F21 (D+) instruction instead of F20 (+), be sure to convert the 16-bit addend and augend
into 32-bit data using the F89 (EXT) instruction.
If an overflow or underflow occurs, the carry flag (special internal relay R9009) will turn on.
Flag conditions
・Error flag (R9007): Turns on and stays on when the area specified using the index modifier
exceeds the limit.
・Error flag (R9008): Turns on for an instant when the area specified using the index modifier
exceeds the limit.
・= flag (R900B): Turns on for an instant when the calculated result is recognized as “0.”
・Carry flag (R9009): Turns on for an instant when the calculated result exceeds the range of 16-bit
data (overflows or underflows).
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