Sequencer Instructions
Chapter 15
155
NOTE: When the rung is false, data is not transferred by the instruction
and outputs remain in their last state unless changed by instructions
elsewhere in the user program.
A mask is a means of selectively screening out data. The purpose of the
mask in the Sequencer Output instruction is to allow unused bits of output
words specified in the instruction to be used for other purposes.
The Sequencer Output instruction operates through the output word(s)
specified in the instruction. The number of output bits required for
sequential operations can be less than 16, 32, 48 or 64 corresponding to a
1-, 2-, 3-, or 4-word Sequencer instruction. When this is true, masking
allows the unused output terminals of a module that is specified in the
Sequencer instruction to be used for other purposes.
A zero in a mask bit location prevents the instruction from operating on the
data in the corresponding bit location. A 1 in a mask bit location allows the
corresponding bit to be operated upon. When all the output data bits are
relevant to the instruction, a mask of all ones should be used.
A mask word must be specified for each output word used in the
instruction. When the first mask word address is entered, the industrial
terminal will automatically assign the next 1, 2 or 3 consecutive word
address(es) for the required number of mask words.
WARNING: When choosing a mask word address, be sure
that the next 1, 2 or 3 consecutive word addresses are not
already assigned. Other data written into a mask could cause
undesirable machine operation. Damage to equipment and/or
personal injury could result.
The example in Figure 15.4 shows the result of masking the transfer of
data bits. Although a mask contains 16 bits, 8 bits are used for the purpose
of the illustration.
If a changing mask is desired for different steps of the Sequencer, Get/Put
transfer or File-to-File move can be used to change the mask.
15.1.3
Masking Output Data
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