Chapter
4
41
Introduction to Programming
The user’s program is a group of ladder diagram and functional block
instructions used to control an application. It is initially entered in memory
using an industrial terminal.
Assuming that the data table size has not been changed from
factory-configured values, the user program begins after word address
177
8
.
In certain applications, this area of PLC-2/30 memory can further be
divided into data highway instructions, main ladder diagram program and
subroutine area.
Some of the simple program instructions, such as Examine On, use one
word of memory. Others, such as File instructions, are more complex and
can use two or more words of user program memory. As the user program
is entered from the industrial terminal, the number of words is indicated at
the right of the END statement (including data table words). The words
remaining in memory can be determined by subtracting that number from
the total memory available.
The text of this manual uses the following notational conventions to aid
you when entering commands through the keyboard of the industrial
terminal.
A word in the brackets represents a single key you would press, such as
[ESC] or [RETURN].
Capital letters not in brackets would be entered as shown.
Punctuation such as commas and arithmetic symbols such as = would be
entered as shown.
These brackets < > define copy that must be entered in proper form, not
as printed. For example <message number> means that you enter the
desired number, not the word’s message number.
The industrial terminal responds to your commands, either by displaying
prompts or by displaying information resulting from your commands.
Examples of displayed information are shown the way they would be
displayed by an industrial terminal.
4.0
General
4.1
Notational Conventions
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