Phonetics Sensaphone SCADA 3000, User Manual

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Figure 11: Ladder Bits form
Ladder Program Performance
The execution time of the Ladder Program will depend on several factors. For example, simple
on/off instructions will run faster than mathematical functions. The sequence of events when
the ladder program runs goes like this: (1) Scan all inputs, (2) Run ladder Program, (3) Update
outputs. Listed below are some typical time requirements for estimating the total run time of a
ladder program.
Input Scan
Main Board (all 16)
5.0ms (digital), 12.5ms (analog)
Universal Input Module 3.5ms per module
Pulse Count Module 3.2ms per module
Run Ladder Program
100 instruction program
2.2ms per 100 instructions
Update Outputs
Main Board Relays (all 8)
1.0ms
Relay Output Module 0.9ms per module
Analog Output Module 2.4ms per module
examples
Program A (small) Total Run Time
Main Board with no modules 8.2ms or 122 scans per second
All inputs are digital
100 instruction ladder program.
Program B (medium) Total Run Time
Main board using all analog 23.8ms or 42 scans per second
inputs plus a Universal Input
Module and an Analog Output
Module plus a 200 instruction
ladder program
15-25
Chapter 15: Ladder Logic Programming