Using 1/2ćslot addressing – Rockwell Automation 1785-LTx,D17856.2.1 Classic PLC-5 Programmable Controllers Users Manual User Manual

Page 50

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Assigning Addressing Modes,

Racks, and Groups

Chapter 4

4-8

Using 1/2ĆSlot Addressing

When you select 1/2-slot addressing, the processor addresses one-half of
an I/O module slot as one I/O group. Each physical slot in the chassis
corresponds to two input and two output image-table words. The type
(unidirectional or bidirectional) and density of the module that you install
determines the number of bits that are used in each word.

I I OO

2

3

0

1

Not

Used

Always

0

0

1

2

3

4

5

6

7

0

1

2

3

4

5

6

7

4

5

6

7

Word #

Word #

Output Image Table

Input Image Table

14974

I/O Group Designation

Input/Output Designation

I/O Chassis with 1/2ĆSlot Addressing

You can mix 8-, 16- and 32-pt I/O modules
in any order in the I/O chassis because 32
input bits and 32 output bits are available in
the image table for each I/O slot. When you
use 8- and 16-pt I/O modules with 1/2-slot
addressing, however, you use fewer total I/O
bits in our image table.

Input Word 0

Output Word 0

ImageĆ Table

Words Allocated

for I/O Group 0

Input Word 1

Output Word 1

ImageĆ Table

Words Allocated

for I/O Group 1

#

00

02

04

06

-

10

12

14

16

-

00

02

04

06

-

10

12

14

16

-

#

01

03

05

07

-

11

13

15

17

-

01

03

05

07

-

11

13

15

17

-

Unused

17

0

10 7

17

10

0

7

17

10

0

7

17

10

0

7

Unused

1/2-Slot

I/O Group

0

1/2-Slot

I/O Group

0

1/2-Slot

I/O Group

1

1/2ĆS lot

I/O Group

1

Input

Input

1/2ĆSlot I/O Group with One 32Ćpt Input Module

This I/O group uses two words of the image table.

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