Bradley Smoker PLC-5 user manual Example of Efficient I/O Image Table Use

4-6Addressing I/O and Controller Memory

When planning your system design, consider the densities of the I/O modules you are using and choose an addressing mode that most efficiently uses controller memory.

Example of Efficient I/O Image Table Use.

Input	Output
Terminals	Terminals
00	00
01	01
02	02
03	03
04	04
05	05
06	06
07	07
10	10
11	11
12	12
13	13
14	14
15	15
16	16
17	17

Group 0

16-point I/O modules occupy 16 bits, an entire word, in the image table.

Installing as a pair a 16-point input module and a

16-point output module efficiently uses the image table.

2-slot addressing (2 I/O chassis slot = 1 I/O group = 1 input image word and 1 output image word = 16 input bits and 16 output bits.)

Controller memory

Rack x

	Output Image Table
Word #
0
1
2
3
4
5
6
7
17		00	bits
	Input Image Table
Word #
0
1
2
3
4
5
6
7
17		00	bits

Define the addressing mode for each I/O chassis by setting the chassis backplane switch assembly. For more information, see Appendix E.

Publication 1785-UM012D-EN-P - July 2005