Calculating the Minimum MAST Cycle Time
Original instructions
About us
Introduction
By configuring a sufficiently large MAST cycle time, the PLC in your Quantum EIO system can process all the data produced by the system in a single scan. If the configured MAST cycle time is smaller than the required processing time, the CRP/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
The formula you can use to estimate minimum MAST cycle time is as follows:
5 * ((# of drops) * ((average input process time / drop) + (average output process time / drop))
In the above formula, the processing times per drop depends upon the average input size and the average output size (in bytes), as follows:
Average Size of Input/Output per Drop
Input Processing Time (ms)
Output Processing Time (ms)
20
0.290
0.283
40
0.314
0.298
64
0.342
0.317
128
0.417
0.367
200
0.501
0.423
300
0.678
0.662
400
0.795
0.740
500
0.912
0.819
600
1.089
1.058
700
1.206
1.136
800
1.382
1.375
900
1.500
1.453
1000
1.617
1.531
1100
1.793
1.770
1200
1.911
1.848
1300
2.087
2.087
NOTE: You can determine the average input and the average output size per drop in Control Expert. For information on how to do this, refer to the Configuring the Size and Location of Data topic in the Quantum EIO Remote I/O Modules Installation and Configuration Guide.
Example:
In this example, the configuration consists of:
The minimum MAST cycle time equals:
5 * 10 (0.314 + 0.283) = 29.85 ms