lecture 9 sequencer

7/31/2019 Lecture 9 Sequencer

http://slidepdf.com/reader/full/lecture-9-sequencer 1/10

ECT 464

Lecture 9

Sequencer



Today’s Quote:

Feed your faith and your doubtswill starve to death.

But we are not of those who shrink back and are destroyed, but of those who

believe and are saved. Hebrews 10:39



Sequencer Overview

• Sequencer instructions are used to controlautomatic assembly machines or

processes that have a consistent andrepeatable operation. They are typicallytime based or event driven.



Sequencer Instructions

• Sequencer Compare

• SQO - Sequencer Output

• SQL - Sequencer Load

• Use the sequencer compare instruction todetect when a step is complete; use thesequencer output instruction to set outputconditions for each step. Use the

sequencer load instruction to load datainto the sequencer file.



Sequencer Compare (SQC)

• On a false-to-true rung transition, the SQC

instruction is used to compare maskedsource words with the masked value at areference address (the sequencer file) for

the control of sequential machineoperations.



SQC Mask • When the status of all non-masked bits in the

source word match those of the correspondingreference word, the instruction sets the foundbit (FD) in the control word. Otherwise, thefound bit (FD) is cleared.

• The bits mask data when reset (0) and passdata when set (1).

• The mask can be fixed or variable. If you enter

a hexadecimal code, it is fixed. If you enter anelement address or a file address (direct orindirect) for changing the mask with each step,it is variable.



SQC Increment

• When the rung goes from false-to-true, the

instruction increments to the next step (word)in the sequencer file. Data stored there istransferred through a mask and compared

against the source for equality. While the rungremains true, the source is compared againstthe reference data for every scan. If equal, theFD bit is set in the SQC control counter.

• Applications of the SQC instruction include

machine diagnostics.



Sequencer Output (SQO)• On a false-to-true rung transition, the SQO

instruction transfers masked source referencewords or long words to the destination for thecontrol of sequential machine operations. Whenthe rung goes from false-to-true, the instruction

increments to the next step (word) in thesequencer file. Data stored there is transferredthrough a mask to the destination addressspecified in the instruction. Data is written to the

destination word every time the instruction isexecuted.



Sequencer Output (SQO)



Sequencer Load (SQL)

• On a false-to-true rung transition, the SQL

instruction loads words into a sequencer file ateach step of a sequencer operation.

lecture 9 sequencer

Documents