Using 1/2ćslot addressing – Rockwell Automation 1785-LTx,D17856.2.1 Classic PLC-5 Programmable Controllers Users Manual User Manual
Page 50
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.