Dear all,

I am looking for software to calculate Foundation Fieldbus H1 microcycle. Any tips will be appreciated.

Thanks in advance,

Ricardo Almarza

 

There is no generic software available to estimate schedule macrocycle. The exact macrocycle schedule is determined by the control system engineering software.

The macrocycle schedule consists of a real-time (RT) slots and a non-real-time "background" slot (NRT). The amount of time allocated is unique to each control system. Some systems have "optimization" algorithms to ensure control response and display update are ideal.

For engineering purposes it may be a good idea to experiment with the system you have to see what macrocycle you get with different loading. Based on this you get rules of thumb such as: * For 250 ms: 1 loop (valves) + 9 transmitters * For 500 ms: 2 loops (valves) + 8 transmitters * For 1000 ms: 3 loops (valves) + 7 transmitters

You can do this offline (without devices connected) because all the timing data required by the engineering tool is in the EDDL and CFF files.

Depending on if you do Control-in-the-Field (CIF) or Control-in-the-Controller (CIC) you get different macrocycle. Some systems read monitoring transmitters RT others use NRT so this makes a difference. Function block execution time also plays a large role. Use fast devices for short control period.

Cheers,
Jonas