Publication 1763-RM001C-EN-P - October 2009
228
File Instructions
BSR - Bit Shift Right
Instruction Type: output
If you wish to shift more than one bit per scan, you must create a loop in
your application using the JMP, LBL, and CTU instructions.
The BSR instruction loads data into a bit array on a false-to-true rung
transition, one bit at a time. The data is shifted right through the array,
then unloaded, one bit at a time. The following figure shows the
operation of the BSR instruction.
This instruction uses the following operands:
•
File - The file operand is the address of the bit array that is to be
manipulated.
•
Control - The control operand is the address of the BSR’s control
element. The control element consists of 3 words:
•
Bit Address - The source is the address of the bit to be transferred
into the bit array at the last (highest) bit position.
EN
DN
BSR
Bit Shift Right
File
#B3:3
Control
R6:0
Bit Address
I:0/15
Length
1<
BSR
Execution Time for the BSR Instruction
Controller
When Rung Is:
True
False
MicroLogix 1100
34.5
μ
s + 0.2
μ
s/word
34.5
μ
s
Data block is shifted one bit at
a time from bit 69 to bit 32.
Source Bit
I:23/06
38 Bit Array
#B3:2
Unload Bit
(R6:0/10)
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
48
INVALID
69
68
67
66
65
64
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Word 0
EN
(1)
(1) EN - Enable Bit is set on false-to-true transition of the rung and indicates the instruction is enabled.
--
DN
(2)
(2) DN - Done Bit, when set, indicates that the bit array has shifted one position.
--
ER
(3)
(3) ER - Error Bit, when set, indicates that the instruction detected an error such as entering a negative number for the
length or source operand.
UL
(4)
(4) UL - Unload Bit is the instruction’s output. Avoid using the UL (unload) bit when the ER (error) bit is set.
not used
Word 1
Size of bit array (number of bits).
Word 2
not used
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