Automating Manufacturing Systems - Process Control and ...

plc function ref - 34.6
CTD - CounT Down
A
CTD
COUNT DOWN
Counter C5:0
Preset 50
Accum. 0
Description:
The counter accumulator will decrease once each time the input goes from
false to true. If the accumulator value reaches the preset the done bit,
DN, will be set. The accumulator value will still decrease even when the
done bit is set
Status Bits:
Registers:
CU
CD
DN
OV
UN
ACC
PRE
Not used for this instruction
Will be true when the input is true
Will be set when ACC < PRE
Not used for this instruction
Will be set if the counter value has gone below -32,768
The time that has passed since the input went true
The maximum time delay before the timer goes on
Available on: Micrologix, PLC-5