Controllogix - simple question about periodic tasks

[valter.carvalho]

Hi everyone,


Suppose I have a periodic task to trigger some communications, and in this task I have a pointer that iterates for each communication trigger (which goes to it's respective MSG).
The iteration is a simple addition to the pointer number, then the routines with the MSG's are called, then the next and after the last one I move zero to the pointer.


Question is: In a periodic task, the pointer will only iterate once each time the task is called?
For example, my periodic task runs each 100ms. I have a pointer to cycle through 12 msg blocks. Can I assume the task will execute one iteration per 100ms, which will give me a span time of 1200ms between a message A is executed, then the other ones, and finally message A is executed again?


Or if the total running time of the task is, for example 10ms, it will cycle many times until it's 100ms window finishes?

 

[Jim3846]

If this is a low priority task then use timers in a continuous task to call the printer. Otherwise the periodic task has priority over the continuous task off the bat.

There is a doc that explains the basic concepts of what each type of task represents.
Basic concept below
Continous - lowest
Periodiic - next
Interrupt - next
Motion - highest.

There is a 1 to 10 value that gives you priority within each type.

 

[Operaghost]

In a periodic task it will run through the code one time for each period. If you want to have it trigger each message on every scan, then we need to rethink how the logic executes and how the pointer increments.

OG

EDIT: The periodic rate is how often the task will execute. Not how long it will execute. Assuming no other tasks, if it takes 10ms to run the task one time, then after it executes it will return to the continuous task and resume scanning. 90ms later it will generate the periodic interrupt again. For multiple tasks, priorities are selected from 1-15 with 1 being the highest priority. So a periodic priority of 1 is higher priority than an EVENT task with a priority of 2. The continuous task has no priority (think 16).

 

[valter.carvalho]

That's what I needed to know. Very thank you!