Sequencer Instructions
Chapter 15
154
Figure 15.3
Sequencer Output Analogy
1
0
1
1
1
1
0
1
1
0
1
1
0
1
0
0
1
2
3
4
5
6
Step
Equivalent
Sequencer
Table
Bit Locations
Peg Locations
1
2
3
4
5
6
Rotation
Drum
Cylinder
Step
When the rung containing the Sequencer Output instruction goes from
false to true, the counter increments to the next step in the sequencer
table. The data found there is output to the output word address that was
specified in the Sequencer instruction. The output word addresses need not
be consecutive.
The Sequencer Output instruction operates whenever the rung is true. This
means that once the rung is enabled, the counter is incremented to the next
step and the data in that step will be outputted every scan that the rung
remains true. The instruction will not advance to the next step until there is
a false-to-true transition of the rung condition.
When the last step of the sequencer table is outputted (AC= PR), the Done
bit is set. The next false-to-true transition of the rung condition will start
the instruction operation again at step 1. The instruction counter should be
set to zero for start-up purposes if it is desirable to start at step 1 when the
instruction is enabled for the first time.
15.1.2
Operation of the Sequencer
Output Instruction
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