Allen-Bradley 1747-SN User Manual page 47

4–2 Scanner Configuration and Programming
Bit Number (decimal)
Logical Rack 0 Group 0
Logical Rack 0 Group 1
Logical
Logical Rack 0 Group 2
Logical Rack 0 Group 3
Rack 0
Logical Rack 0 Group 4
Logical Rack 0 Group 5
Logical Rack 0 Group 6
Logical Rack 0 Group 7
Logical Rack 1 Group 0
Logical Rack 1 Group 1
Logical
Logical Rack 1 Group 2
Logical Rack 1 Group 3
Rack 1
Logical Rack 1 Group 4
Logical Rack 1 Group 5
Logical Rack 1 Group 6
Logical Rack 1 Group 7
Logical Rack 2 Group 0
Logical Rack 2 Group 1
Logical
Logical Rack 2 Group 2
Logical Rack 2 Group 3
Rack 2
Logical Rack 2 Group 4
Logical Rack 2 Group 5
Logical Rack 2 Group 6
Logical Rack 2 Group 7
Logical Rack 3 Group 0
Logical Rack 3 Group 1
Logical
Logical Rack 3 Group 2
Logical Rack 3 Group 3
Rack 3
Logical Rack 3 Group 4
Logical Rack 3 Group 5
Logical Rack 3 Group 6
Logical Rack 3 Group 7
Bit Number (octal)
Publication 1747 6.6 - July 1996
The illustration below shows how logical racks, logical groups, and
words are allocated within the I/O image files. Note that this
illustration describes the input image file. The scanner's output
image file is the same, except that its addressing scheme starts with
O:e.0 and ends with 0:e.31.
e = slot number of the SLC chassis containing the scanner
15 14 13 12
Word 0
Word 1
Word 2
Word 3
Word 4
Word 5
Word 6
Word 7
Word 8
Word 9
Word 10
Word 11
Word 12
Word 13
Word 14
Word 15
Word 16
Word 17
Word 18
Word 19
Word 20
Word 21
Word 22
Word 23
Word 2 4
Word 25
Word 26
Word 27
Word 28
Word 29
Word 30
Word 31
17 16 15 14
8 8 8 8
The 1747-SN Scanner's I/O image structure is described below:
The I/O image file consists of four logical racks (numbered 0,1,2,
and 3) of input image and four logical racks of output image.
Each logical rack consists of eight logical groups
(numbered 0, 1, 2, 3, 4, 5, 6, and 7).
Each logical group consists of two words (an input word and an
output word).
Each word consists of two bytes (a high and a low byte). Low
byte is bits 0–7 and high byte is bits 8–15.
Each byte consists of 8 bits with each bit having the ability to
control one discrete I/O point.
11 10 9 8 7 6
13 12 11 10 7 6
8 8 8 8 8 8
5 4 3 2 1 0
5 4 3 2 1 0
8 8 8 8 8 8
SLC Input
File Address
I:e.0
I:e.1
I:e.2
I:e.3
I:e.4
I:e.5
I:e.6
I:e.7
I:e.8
I:e.9
I:e.10
I:e.11
I:e.12
I:e.13
I:e.14
I:e.15
I:e.16
I:e.17
I:e.18
I:e.19
I:e.20
I:e.21
I:e.22
I:e.23
I:e.24
I:e.25
I:e.26
I:e.27
I:e.28
I:e.29
I:e.30
I:e.31