Panasonic FP Series

Appendix Programming Information
1252
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
32767
7FFF
1
0
-1
16# 0001
16# 0000
16# FFFF
-32767 8000
IX value
Max. value
Min. value
Overflow
Underflow
Maximum and minimum
values form a loop
Example 1: 32767 + 1 (overflow)
The result of processing will be K-32768 and the carry flag will turn ON.
Example 2: -32768 - 1 (underflow)
The result of processing will be 32767 and the carry flag will turn ON.
BCD 4-digit processing
16#9999
16#0
Max. value
Min. value
Overflow
Underflow
Maximum and minimum
values form a loop
Example 1: 16#9999+ 16#1 (overflow)
The result of processing will be 16#0 and the carry flag will turn ON.
Example 2: 16#0 - 16#1 (underflow)
The result of processing will be 16#9999 and the carry flag will turn ON.