Chapter
21
21-1
Sequencers
This describes the three types of sequence instructions:
sequencer input
sequencer output
sequencer load
These instructions either transfer information from the data table to output
word addresses, compare I/O word information with information stored in
tables, or transfer I/O word information into the data table.
Sequencer instructions are similar to file instructions but have some
marked differences. Both are block instructions that contain a counter and
a file. The instructions require the entry of more than one address. Each
has a corresponding data monitor display for monitoring, loading or editing
file data.
File instructions operate on files that are 1 word (16 bits) wide. In
contrast, sequencer instructions operate on files that are as many as
4 words (64 bits) wide with as many as 999 rows. A sequencer file can be
represented graphically by a sequencer table (Figure 21.1.)
Figure 21.1
Sequencer Table
Step Word 1 Word 2 Word 3 Word 4
001
002
003
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00110101 11000101 00011101 11001010 10111011 11001011 01011101 01011111
01110100 00011101 00010111 00110011 01010101 01010101
00010101 10100000 10100010 10101000 01010000 01011111 10111100 00110011
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Important: The sequencer’s data table is one word wide by many long.
A sequencer table appears in the data table as one continuous file. The
length of the file in the data table equals the product of the number of steps
and the length as shown in Figure 21.2. As an example, a 24 step x 4 word
wide sequencer table occupies 96 consecutive words in the data table.
Chapter Objectives
Comparison with File
Instructions
