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This is a multi-scan instruction, and because
it takes multiple scans to complete, it cannot be used in either Subroutines or Interrupt
Service Routines. It can used in Programs and under special
circumstances can also be used in Stages inside of a Program or in Tasks. See the help topic “Instruction Set Chart”
for more information. This counter has 3 input rungs. One for both UP and One for down and down
input. Both of these are edge triggered. This is indicated by the arrow on the input
leg. The third input would be the Reset rung. When the reset is true, the counter will reset
to zero. Notice that this counter has two preset one
for up count and one for down count. When the count is equal or greater that the
up preset, the .done bit will turn on. When the count is equal to or less than the
down preset, the down DONE bit will turn on.