User`s manual

GFK-1742A 10-1
Introduction to Local Logic Programming
This chapter contains an introduction to the basic local logic programming concepts. The DSM
and the DSM motion programming language are not discussed in detail in this chapter. These
concepts are discussed in other chapters within this manual.
Introduction to Local Logic Programming
The local logic program works in conjunction with the PLC logic program and motion program to
yield a flexible programming environment. Specifically, local logic programs provide the user
with the ability to perform math and logic that is deterministic and synchronized with the DSM
Position Loop execution rate. This ability is critical to many applications where the accuracy
and/or speed require this tight synchronization.
The DSM local logic function provides the user the ability to execute basic logic and mathematical
functions within the DSM module. Additionally, local logic permits fast read/write access to local
DSM digital and analog I/O. Consult Chapter 14 and Chapter 15 for a complete listing of available
I/O. The local logic program execution method guarantees the local logic program runs at the
position loop sample rate and completes each sample period. Note: If the module is unable to
complete the local logic program execution within the allotted time the module generates an error
message. Chapter 13 and Appendix E contain more information concerning program execution
times. Additionally, the local logic program runs in parallel with normal DSM motion programs.
The parallel program execution allows the local logic program to supervise the motion program.
Thus, local logic programs are also called supervisory logic blocks (SLB). The local logic program
execution versus motion program execution is shown in Figure 10-1.
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Chapter