drbitboy
Lifetime Supporting Member
Does anyone know the history of the A-B 10kHz free-running clock?
It seems to only exist in the MicroLogix 1xxx line: S:4 is the 16-bit clock itself; S:35 is the duration of the last scan in 100us steps. Why is it not available in all PLCs?
The free-running clock is very useful: S:35 can be used to implement a repeating timer functionality that triggers as reliably as possible in real-time. Of course the accuracy of any one trigger is no better one scan time plus any drift in the clock's base oscillator, but the mean period will be precise wrt the target. A TON will always run slower than what is specified in the .PREset.
It seems to only exist in the MicroLogix 1xxx line: S:4 is the 16-bit clock itself; S:35 is the duration of the last scan in 100us steps. Why is it not available in all PLCs?
The free-running clock is very useful: S:35 can be used to implement a repeating timer functionality that triggers as reliably as possible in real-time. Of course the accuracy of any one trigger is no better one scan time plus any drift in the clock's base oscillator, but the mean period will be precise wrt the target. A TON will always run slower than what is specified in the .PREset.