Publication 1762-RM001C-EN-P
Timer and Counter Instructions 8-9
CTU - Count Up
CTD - Count Down
Instruction Type: output
The CTU and CTD instructions are used to increment or decrement a
counter at each false-to-true rung transition. When the CTU rung makes a
false-to-true transition, the accumulated value is incremented by one
count. The CTD instruction operates the same, except the count is
decremented.
CU
DN
CTU
Count Up
Counter C5:0
Preset 0<
Accum 0<
CTU
CU
DN
CTU
Count Down
Counter C5:0
Preset 0<
Accum 0<
CTD
Table 8.14 Execution Time for the CTU and CTD Instructions
Controller CTU - When Rung Is: CTD - When Rung Is:
True False True False
MicroLogix 1200 9.0
µ
s9.2
µ
s9.0
µ
s9.0
µ
s
MicroLogix 1500 6.4
µ
s8.5
µ
s7.5
µ
s8.5
µ
s
NOTE
If the signal is coming from a field device wired to an
input on the controller, the on and off duration of the
incoming signal must not be more than twice the
controller scan time (assuming 50% duty cycle). This
condition is needed to enable the counter to detect
false-to-true transitions from the incoming device.
To Next Page
Loading...
Need help?
General
