Emerson DSM314 User Manual

User Manual Chapter 10
GFK-1742F Jan 2020
Introduction to Local Logic Programming 249
10.2 When to Use Local Logic Versus Ladder Logic
The local logic programming language contains basic mathematical and logical constructs.
The capabilities are not designed to replace the host controller’s logic capabilities. Instead,
local logic is designed to complement the host controller’s logic and mathematical abilities.
Specifically, local logic is designed to solve a small logic and mathematical set that requires
tight synchronization with the controlled motion. The local logic program must run to
completion each sample period. Thus, local logic programs are limited in size. The default
local logic program size limit is 150 lines. The Local Logic build process will generate an error
message when the 150-line limit is exceeded. A warning message is generated when 100
lines are exceeded. If the program is very large and computationally intensive it may exceed
the allowed execution time and result in a watchdog timer warning/error (refer to Appendix
E). In contrast, the host controller’s program size is limited only by available memory.
However, as host controller program sizes increase, the host controller sweep times
increase. (For additional information concerning sweep times, please consult the
PACSystems CPU Reference Manual, GFK-2222 or the Series 90-30/20/Micro PLC CPU
Instruction Set Reference Manual, GFK-0467.) This is not true with local logic programs.
Local Logic programs always execute to completion every position loop sample period.
When using host controller logic, the added latency associated with the host controller
sweep times for time-critical logic operations that are tightly coupled to motion can be
unacceptable or limit process performance. These tightly coupled and time-critical
processes are potential Local Logic applications. Each process will have to be evaluated on
an individual basis to determine which sections to write in host controller logic and which
sections to write in Local Logic.
10.3 Getting Started with Local Logic and Motion
Programming
The sections that follow provide information on getting started with the Local Logic Editor
and Motion program editors. The sections concentrate on program usage with an emphasis
on program creation, syntax check, and program download.
10.3.1 Requirements
The Local Logic and Motion Program editors are integrated within the programming
software environment. You need one of the following software packages. Please refer to the
software documentation for installation instructions.
•
Machine Edition Logic Developer – PLC version 2.1 or later
•
VersaPro version 1.1 or later (Series 90-30 only. For details, refer to Appendix H.)
The DSM314 feature set also requires:
— PACSystems firmware release 2.8 or later, or
— 90-30 CPU firmware release 10.0 or later.

Emerson DSM314 Specifications

General

Brand	Emerson
Model	DSM314
Category	Controller
Language	English