Chapter
15
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Sequencer Instructions
Sequencer Instructions are powerful block instructions. They operate on
up to 4 words (64 bits) at a time. There are three sequence instructions:
Sequencer Output, Sequencer Input and Sequencer Load.
Sequencer instructions can be used to transfer information from the data
table to output word addresses for the control of sequential machine
operation (Sequencer Output); to compare I/O word information with
information stored in tables so that machine operating conditions can be
examined for control and diagnostic purposes (Sequencer Input); and to
transfer I/O word information into the data table (Sequencer Load). When
used in combination or with other instructions, the potential to create
powerful, concise programs is nearly unlimited.
NOTE: This section assumes the reader has read Chapter 12, Data
Transfer File Instructions and is familiar with the concepts and terms
introduced in that chapter.
Comparison With File Instructions
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 one word or 16 bits wide. In
contrast, Sequencer instructions operate on files that are up to four words
or 64 bits wide. A sequencer file can be represented graphically by a
sequencer table. The length or number of steps (rows) in a sequencer table
can be up to 999. The width of a sequencer table can be up to four words
(columns) as shown in Figure 15.1.
NOTE: The 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 equals
the product of the number of words wide (columns) and the number of
steps as shown in Figure 15.2. As an example, a 24-step by 4-word-wide
sequencer table will occupy 96 consecutive words in the data table.
Internally indexed file instructions, when enabled, perform the operation
and then increment to the next step. In contrast, internally indexed
15.0
General
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