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PL7 Pro – Addressing BITS AND WORDS Objects

GENERAL PRESENTATION

WHAT IS AN OBJECT

An object is an entity that can be manipulated by program, it can be an input image, part of a timer, part of the system, part of communication, etc.

REPRESENTATION OF OBJECTS

Objects are represented by the symbol “%” followed by one or two letters specifying their type and then a letter specifying their format (bits, byte, words, double, real etc.)

LIST OF DIFFERENT TYPES OF OBJECTS

DFB types (No format precision)

OBJECT FORMATS

THE ELEMENTS OF OBJECTS

Most objects are made up of several elements or sub-elements, for example, a counter contains a current value, a preset value, two overflow bits and one preset bit reached

Discrete input cards have bits representing the physical states of the sensors, but also a module fault bit and a fault bit per channel, some cards also have words or tables of words representing their states or their configurations.

We access an element of an object by putting a period behind the number of the object then the identifier of the element (a number or a reserved symbol), then if the element contains other sub-elements we add a dot followed by the Identifier etc.

CARD OBJECTS

To identify an object on a card, you must specify its module number then the channel number.

If several objects are associated with a channel, the object number must be specified. (except for object N ┬░ 0)

Examples:% IW0.12.2 Word 2 of channel 12 of module 0

% IW0.12 Word 0 of channel 12 of module 0

STRUCTURED OBJECTS

(bits extracted from words, tables of bits, tables of words)

BIT EXTRACT FROM WORDS

BIT TABLES OR BIT STRINGS

TABLE OF WORDS

Example objects of an entry card at slot 4

FORMS OF ADDRESSING

DIRECT ADDRESSING

Example of direct address:% MW20

The address is fixed, and defined by program.

THE INDEX ADDRESS

The direct address is completed with an index, contained in a word.

EXERCISE 1 ADDRESSING OBJECTS

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