By configuring a sufficiently large MAST cycle time, the in your M580 system can process the data processed by the system in a single scan. If the configured MAST cycle time is smaller than the required processing time, the CPU will force MAST to over-run.
By using the formulas (set forth below) to compute a minimum MAST time for your system, you can avoid a MAST overrun situation.
Calculating a Minimum MAST Cycle
Assuming that only the MAST task is configured, the minimum MAST cycle time (in ms) can be calculated as follows:
The minimum cycle time for other tasks can similarly be estimated:
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FAST task: (# of drops using FAST task) / 1.5
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AUX0 task: (# of drops using AUX0 task) / 1.5
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AUX1 task: (# of drops using AUX1 task) / 1.5
If multiple tasks need to be configured, satisfy the following conditions (where all cycle times are measured in ms):
(# of drops using MAST task) / (MAST cycle time) + (# of drops using FAST task) / (FAST cycle time) + (# of drops using AUX0 task) / (AUX0 cycle time) + (# of drops using AUX1 task) / (AUX1 cycle time) < 1.5
If DIO devices are configured, the minimum cycle time needs to be increased.
NOTE:
If you add a BME CXM 0100 module to the rack in Control Expert, you choose either Remote or Distributed.
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If you choose Remote , then the BME CXM 0100 module acts like a drop in the statement (# of drops using MAST task) / 1.5) in the way that MAST cycle is affected.
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If you choose Distributed, then the BME CXM 0100 module acts like a distributed device in the statement (If DIO devices are configured, the minimum cycle time needs to be increased.)
Unlike an actual drop, the BME CXM 0100 module can be mapped only to the MAST task.
In this example, the configuration consists of:
The minimum MAST cycle time equals:
10 / 1.5 = 6.7 ms
