copyright © 2002 delmar thomson learning chapter 17 sequencer instructions

Copyright © 2002 Delmar Thomson Learning

Chapter 17

Sequencer Instructions


Objectives

Describe the function of a sequencer.

Describe the operation of the SLC 500 sequencer output (SQO) instruction.

Explain the function of each SQO status bit.


Objectives (cont’d.)

Explain the role of the control (R6) file.Explain the role of the bit file while

programming a sequencer instruction.Explain what a mask is and why it is

used.Determine the appropriate hexadecimal

mask for your application.


Sequencer Instructions


Sequencer Output Instruction (SQO)

SQO is an output instruction.Each false to true transition causes

the SQO instruction to increment to the next sequence step.

Sequencer steps are stored in a reference data file.


SLC 500 PLC Sequencer Output

Instruction


Bit File Containing Sequencer Step Data


Sequencer Operation


Sequencer Reference File #B3:0


SQO Control File

Sequencer instructions do not have designated data files like timers or counters.

Use R6 control file.Control file will store sequencer

status bits, length, and position data.


Three-Word Control Element for the SQO


SQO and Associated Status Bits


SQO and Hexadecimal Masking

Sequencers use hexadecimal masks similar to the MVM instruction to filter data from the sequencer reference file to the output destination.


Only Bits 0 through 7 Will Be Allowed to Pass through the

Mask


Only Bits Set to a 1 Will Allow Data to Pass


Bit Pattern Translated to Hexadecimal


Only Bits 8 through 11 Will Be Allowed to Pass through the

Mask


Selected Single Mask Bits Set to a 1


Bit Pattern Translated to Hexadecimal


Binary Bit Pattern and Hex Correlations

copyright © 2002 delmar thomson learning chapter 17 sequencer instructions

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