Bradley Smoker PLC-5 user manual This Capability Lets You, Mcp

1-10Understanding Your Programmable Controller

Programming Features

This table highlights the programming features of a PLC-5 programmable controller.

This Capability	Lets You
Ladder logic	program using a language that is representative of relay logic.
	Choose this language
	• if you are more familiar with ladder logic than with programming languages such
	as BASIC
	Your plant personnel may be more familiar with ladder logic; consider their needs
	as well.
	• performing diagnostics
	• programming discrete control
Subroutines	store recurring sections of program logic that can be accessed from multiple program
	files.
	A subroutine saves memory because you program repetitive logic only once. The JSR
	instruction directs the controller to go to a separate subroutine file within the logic
	controller, scan that subroutine file once, and return to the point of departure.
Sequential Function Charts	use sequence-control language to control and display the state of a sequential process.
(SFCs)	Instead of using one long ladder program for your application, divide the logic into steps
	and transitions. A step corresponds to a control task; a transition corresponds to a
	condition that must occur before the programmable controller can perform the next
	control task. The display of these steps and transitions lets you see what state the
	machine process is in at a given time via a flowchart form.
	SFCs offer constructs that enable execution of multiple paths of logic, or a single
	selected path of logic, as well as the ability to jump forwards and backwards.
	Troubleshooting can be reduced to a small routine of logic instead of an entire ladder
	file.
	SFCs are best for defining the order of events in a sequential process.
Structured text	program using a language similar to BASIC.
	Choose structured text if you are:
	• more familiar with programming languages such as BASIC than with ladder logic
	• using complex mathematical algorithms
	• using program constructs that repeat or “loop”
	• creating custom data-table monitoring screens
Main Control Programs	separate sequential logic from ladder logic and structured text as a way of modularized
(MCPs)	your process and making troubleshooting easier.
	Use several main control programs (MCPs) to define one main control program for each
	particular machine or function of your process. MCPs accommodate independent or
	non-sequential activities.
	A main control program can be an SFC file numbered 1-999 or a ladder-logic file or
	structured-text program numbered 2-999.
	One data table is used by all MCPs (i.e., you do not have a separate data table for each
	MCP).

Publication 1785-UM012D-EN-P - July 2005