Rockwell-automation 1772-LV Mini-PLC - 2/15 Programmable Controller (S Manual de usuario descargar pdf (Pagina 45)

Fundamental Instruction Set

Chapter 5

58

The rung below achieves the same result, but avoids nested branching:

110

010

110

Section C

Timers and Counters

Timer and counter instructions are output instructions internal to the controller.

They provide many of the capabilities available with timing relays and solid

state timing/counting devices. Usually conditioned by examine instructions,

timers and counters keep track of timed intervals or counted events according to

the logic continuity of the rung. You can program a maximum of 488 internal

timers and/or counters.

Each timer or counter instruction has two 3-digit values. Each value requires

one word of data table memory. These 3-digit values are:

Accumulated Value (AC)

Storage: Begins at word address 030.

Function: Timers - number of elapsed timed intervals.

Counters - number of counted events.

Both - upper 4 its of accumulated word (14-17) are the status bits.

Preset Value (PR)

Storage: Always 100

words greater than its corresponding AC value.

Function: Denotes the number of timed intervals or events to be counted.

When the accumulated value equals the preset value, AC=PR, a status bit is

set and can be examined to turn an output device on or off.

Introduction

A timer counts elapsed time-base intervals and store this count in the

accumulated value word. Timer instructions have three time bases: 1.0 second,

0.1 second, or 0.01 second.

Introduction

Timer/Counter Theory

Timer Instructions

1 2 ... 40 41 42 43 44 45 46 47 48 49 50 ... 214 215

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Rockwell-automation 1772-LV Mini-PLC - 2/15 Programmable Controller (S Manual de usuario Pagina 45