Allen-Bradley Micro800 2080-MEMBAK-RTC2 User Manual page 43

Rockwell Automation Publication 2080-UM004D-EN-E - March 2018
flag will be set to indicate that a rollunder has occurred. It is reset using the
ResetCountUnderflow_n bit.
MaxCountValue
Count Down
1: linear counter. When the counter is a linear counter and the present count
value is equal to MaxCountValue_n the next input count in the up direction will
activate the CountOverflow_n bit and also the PresentCount_n will remain at
the MaxCountValue_n. CountOverflow_n is reset using the
ResetCountOverflow_n bit.
Conversely, when the PresentCount_n is equal to MinCountValue_n the next
input count in the down direction will activate the CountUnderflow_n bit and
the PresentCount_n will remain at MinCountValue_n. CountUnderflow_n is
reset using the ResetCountUnderflow_n bit.
The counts in overflow and underflow will not be accumulated at all.
IMPORTANT
That is, even if 1000 pulses are applied while in overflow, the first pulse
with the opposite direction (down in this case) will cause the counter to
be decremented by 1. (The CountOverflow_n bit is only reset using the
ResetCountUnderflow_n bit.)
MinCountValue
Count Up
Underflow
High Speed Counter – 2080-MOT-HSC
MinCountValue
Rollover
Count Up
0
Count Down
Chapter 4
MaxCountValue
Overflow
33