PID instruction for SLC 5/03

Hi,

I want to know the difference between Timed Mode and STI Mode for PID instruction.
I’ll use 4 blocks of PID in my program so which Mode helps me more?

Thank you

David1986 said:

Hi,

I want to know the difference between Timed Mode and STI Mode for PID instruction.
I’ll use 4 blocks of PID in my program so which Mode helps me more?

Thank you

Click to expand...

That depends on your circumstances. In timed mode, the PID Instruction updates at the time set in the PID Setup. This may vary a bit depending on Scan Time and other circumstances. In STI Mode, the PID Instruction updates based on a pretty accurate Software Timed Interupt. The PID Instruction Update Time has to be set to the same value as the STI time. If all 4 PID Instructions can work well with the same Update Time, then you could put them all in the same Subroutine, and call it using the STI. If their required Update Times are radically different, then you will have to use Timed Mode. However, you could still set up the most critical PIDs in STI Mode.

Stu....