Page 277 - Programmable Logic Controllers, Fifth Edition - Mobile version

Output module
L2
0
1
SQO 2
SEQUENCER OUTPUT EN
File #B3:0 DN 3
Mask 003Fh
Dest O:2 4
Control R6:0
Length 4 5
Position 1

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
O:2 Destination – – – – – – – – – – 0 0 0 0 0 0

Mask
003Fh (hexadecimal) 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1
11111B (binary)

B3:0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Start

B3:1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1 Step 1
Sequencer
file B3:2 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 Step 2
B3:3 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 Step 3
B3:4 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 Step 4

Figure 12-9 Sequencer moving data through a mask word.

Input Ladder logic program Output
L1 L2
PB1 • When the position parameter reaches 4 (the value
SQO
SEQUENCER OUTPUT EN O:2/0 in the length parameter), all words would have been
PB1 File #B3:0 moved so the DN (done bit) in the instruction is
Mask 3Fh DN O:2/1 set to 1.
Dest O:2 O:2/2
Control R6:0 • On the next false-to-true transition of the rung, with
Length 4 O:2/3 done bit set, the position pointer is automatically
Position 1 reset to 1.
O:2/4
Sequencer instructions are usually retentive, and there
O:2/5
can be an upper limit to the number of external outputs
Positions File #B3:0 O:2 and steps that can be operated on by a single instruction.
1 100001 Destination Many sequencer instructions reset the sequencer automat-
2 010001 ically to step 1 on completion of the last sequence step.
3 001100 Other instructions provide an individual reset control line
4 001010
or a combination of both.
The ControlLogix Sequencer Output (SQO) instruc-
Figure 12-10 Sequencer moving data from a file to an output. tion, shown in Figure 12-11, operates similarly to that of

258 Chapter 12 Sequencer and Shift Register Instructions

pet73842_ch12_252-280.indd 258 03/11/15 7:19 PM