Rockwell Automation 1772-LS_LSP,D17726.8.6 PROG/OPER MANUAL-MINI PLC-2/05 - Manual (Page 129)

Sequencers
Chapter 12
12-3
A 0 in a mask bit location prevents the instruction from controlling or
comparing the data in the corresponding bit location. A 1 in a mask bit
location allows the corresponding bit to be controlled or compared. When
all the output/input bits are controlled or compared by the instruction, use a
mask of all 1’s.
Other instructions can change a mask in the user program. If a changing
mask is required for different steps in the sequencer operation use a get/put
or a file move.
ATTENTION: 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
unpredictable machine operation. This could cause damage to
your equipment and/or injury to your personnel.
Sequencer instructions can be powerful tools when programming your
operations. Two steps in the same instruction can not be operated
simultaneously.
ATTENTION: When programming a sequencer input with a
sequencer output instruction, the counter address for both
instructions must be the same. Failure to use the same counter
address for both sequencers, can result in input and output steps
becoming unsynchronized which may result in unwanted
machine motion and/or injury to personnel.
Use Figure 12.3 while you read about each sequencer instruction.
Programming Limitations
Sequencer Instructions