Micromod Micro-DCI: 53MC5000 Multi-Loop Process Controller FLEXIBLE CONTROL STRATEGIES - Manual (Page 67)

3.2 EXAMPLE 1 - LOGICAL ONESHOT
A logical oneshot can be used to toggle a Contact Closure Output (CCO) or reset a totalizer. As
shown in Figure 3-1, a oneshot pulsed output can be generated from a Logic module. Generating
a pulsed output from a Logic module requires comparing a logical input from the previous scan
with a second logical input from the current scan. This is possible because the individual modules
are executed in the fixed order given in Figures 2-1 through 2-3. This means that those modules
not yet processed in the current scan time still contain outputs from the previous scan iteration.
Therefore, if one input to a Logic module references the output from a subsequent module in the
execution order, it will receive that input value delayed one execution scan. The low-to-high output
pulse transition occurs when the current scan and previous scan inputs are true for the logic func-
tion being performed. The pulse remains high until the previous scan input from the subsequent
module changes. When that module is executed in the current scan the high-to-low pulse transi-
tion occurs.
Figure 3-1. Logical Oneshot
FCS 53MC5000 Flexible Control Strategies
3-2
EX1