Panasonic FP7 User Manual page 71

 Linear counter operation
The overflow or underflow is detected when the count value exceeds the upper or lower limit.
(Example): The following figure shows the time when the underflow occurs. When the
underflow occurs, the elapsed value will be held at the lower limit. Once the underflow clear
signal turns on, the count will restart from the lower limit.
Addition
Counter input
Subtraction
Upper limit
（UM128-UM12F）
Counter elapsed value
0
（UM110-UM117）
Lower limit
（UM120-UM127）
Underflow annunciation
（X20-X27）
Underflow clear
（Y20-Y27）
 Ring counter operation
• If the lower limit is counted down, the count value will be rolled over, and counting down will
continue from the upper limit.
• If the upper limit is counted up, the count value will be rolled over, and counting up will
continue from the lower limit.
Addition
Counter input
Subtraction
Upper limit
（UM128-UM12F）
0
Counter elapsed value
（UM110-UM117）
Lower limit
（UM120-UM127）
7.1 Counter Function
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