Rockwell Automation 1747-PT1, D1747NP002 Hand-Held Terminal - Manual (Page 327)

Chapter 24
Sequencer Instructions
24–5
When the rung goes from false–to–true, the instruction increments to the next
step (word) in the sequencer file. Data stored there is transferred through a
mask to the destination address specified in the instruction. Current data is
written to the corresponding destination word every scan that the rung
remains true.
The done bit is set when the last word of the sequencer file is transferred.
Upon the next false-to-true rung transition, the instruction resets the position
to step one, that is, automatically cycles.
At startup, if the position is = 0 when you switch the processor from the
program mode to the Run mode, instruction operation depends on whether
the rung is true or false on the first scan:
•
If true, the instruction transfers the value in step 0.
•
If false, the instruction waits for the first rung transition from
false–to–true and transfers the value in step 1.
Mask data by resetting bits in the mask word. The bits mask data when reset,
pass data when set. Unless you set mask bits, the instruction will not change
the value in the destination word. The mask can be fixed by entering a hex
code. The mask can be a variable by entering an element address or a file
address for changing the mask with each step. The following figure indicates
how the SQO instruction functions:
SQO
SEQUENCER OUTPUT
File
#B10:1
Mask 0F0F
Dest O:14.0
Control R6:20
Length 4
Position 2
(EN)
(DN)
0000 0101 0000 1010
0 7 8 15
0000 1111 0000 1111
0 7 8 15
0000 0000 0000 0000
1010 0010 1111 0101
1111 0101 0100 1010
0101 0101 0101 0101
0000 1111 0000 1111
0
1
2
3
4
Step
B10:1
2
3
4
5
Word
00
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
ON
ON
ON
ON
External Outputs
associated with O:14
Destination O:14.0
Mask Value 0F0F
Sequencer Output File #B10:1
Current Step
Effect on Index Register in SLC 5/02 Processors
The value present in the index register S:24 is overwritten when the
sequencer output instruction is true. The index register value will equal the
position value of the instruction.