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Appendix Programming Information
40.5 Overflow and Underflow
During execution of a processing instruction, it sometimes happens that the allowed value range is exceeded.
Exceeding the maximum value is called "overflow", and falling short of the minimum value is called "underflow."
If overflow or underflow occurs, the R9009 carry flag CY will turn ON.
40.5.1 Values When Overflow/Underflow Occurs
All of the maximum and minimum values handled by FP series programmable controller's form a loop as shown
in the diagram.
Binary 16-bit processing
Max. value
32767
1
0
-1
-32767
Min. value
Example 1:
The result of processing will be K-32768 and the carry flag will turn ON.
Example 2:
The result of processing will be 32767 and the carry flag will turn ON.
BCD 4-digit processing
Max. value
16#9999
16#0
Min. value
Example 1:
The result of processing will be 16#0 and the carry flag will turn ON.
Example 2:
The result of processing will be 16#9999 and the carry flag will turn ON.
1252
Overflow
7FFF
16# 0001
Maximum and minimum
16# 0000
values form a loop
16# FFFF
8000
Underflow
32767 + 1 (overflow)
-32768 - 1 (underflow)
Overflow
Maximum and minimum
values form a loop
Underflow
16#9999+ 16#1 (overflow)
16#0 - 16#1 (underflow)
IX value
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