Allen-Bradley MicroLogix 1200 Reference Manual page 204

15-4 Sequencer Instructions
Publication 1762-RM001C-EN-P
This instruction uses the following operands:
• File - This is the sequencer reference file. Its contents, on an
element-by-element basis, are masked and compared to the masked
value stored in source.
If file type is word, then mask and source must be
NOTE
words. If file type is long word, mask and source
must be long words.
• Mask - The mask operand contains the mask constant, word, or file
which is applied to both file and source. When mask bits are set to 1,
data is allowed to pass through for comparison. When mask bits are
reset to 0, the data is masked (does not pass through to for
comparison). The immediate data ranges for mask are from 0 to
0xFFFF or 0 to 0xFFFFFFFF.
.
If mask is direct or indirect, the position selects the
NOTE
location in the specified file.
• Source - This is the value that is compared to file.
• Control - This is a control file address. The status bits, stack length,
and the position value are stored in this element. The control element
consists of 3 words:
15 14 13
Word 0 EN (1) -- (2)
DN
Word 1 Length - contains the number of steps in the sequencer reference file.
Word 2 Position - the current position in the sequence
(1) EN - Enable Bit is set by a false-to-true rung transition and indicates that the instruction is enabled.
(2) DN - Done Bit is set after the instruction has operated on the last word in the sequencer file. It is reset on the next
false-to-true rung transition after the rung goes false.
(3) ER - Error Bit is set when the controller detects a negative position value, or a negative or zero length value. When the
ER bit is set, the minor error bit (S2:5/2) is also set.
(4) FD - Found bit is set when the status of all non-masked bits in the source address match those of the word in the
sequencer reference file. This bit is assessed each time the SQC instruction is evaluated while the rung is true.
• Length - The length operand contains the number of steps in the
sequencer file (as well as Mask and/or Source if they are file data
types). The length of the sequencer can range from 1 to 256.
• Position - This is the current location or step in the sequencer file (as
well as Mask and/or Source if they are file data types). It determines
the next location in the stack to receive the current comparison data.
Position is a component of the control register. The position can range
from 0 to 255 for words and 0 to 127 for long words. The position is
incremented on each false-to-true transition.
12 11 10 9 8
-- (3) not used (4)
ER FD
7 6 5 4 3 2 1 0
not used