Allen-Bradley PLC-5 User Manual page 46

4-2 Addressing I/O and Controller Memory
rack number 01
I/O group number 4
Input Module
(1771-IAD)
Notice how input and output
image file addresses
correspond to hardware.
Publication 1785-UM012D-EN-P - July 2005
The figure below shows the relationship between an I/O terminal and its
location in controller memory.
I/O Addressing as It Relates to an I/O Terminal
17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00
Output Image Table
A
B
C
D
17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00
00
01
02
03
04
05
06
07
10
Input Image Table
11
12
13
14
15
04
16
17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00
17
E
I:014
| |
12
I for input or O for output
2-digit I/O rack number
I/O group number (0-7)
input or output number (0-7,10-17) (bit)
Now that you are familiar with how controller memory is segmented to
address a specific I/O terminal, the next section explains available addressing
modes. These modes let you define the relationship between an I/O chassis
slot and an I/O group (16 input bits and 16 output bits).
rack number 01
I/O group number 5
word
address
00
05
07
00
04
Output Module
07
(1771-OAD)
O:015
( )
07
I:014/12
A
B
C
D
00
01
02
03
04
05
06
07
10
11
12
13
14
15
16
17
E
I/O image table is
addressed octally.