Rockwell Automation 2706-MB1 MESSAGEVIEW 421 SOFTWARE MANUAL - Manual (Page 102)

5–13 Communications Overview
Publication 2706-817
Module groups
The MessageView 421 I/O can occupy 1 /
4
, 1 /
2
, 3 /
4
, or a Full rack.
Each 1 /
4
rack contains two module groups (32 input and 32 output
bits). An entire rack contains 8 module groups that are numbered
from 0 to 7.
Rack # MessageView I/O
Four 1/4
Rack Sizes
Eight Input/Output
Module Groups
0 1 2 3 4 5 6 7
1 /
4
1 /
4
1 /
4
1 /
4
Input
Output 0 1 2 3 4 5 6 7
Each input or output module group has 16 bits
If a MessageView terminal does not occupy a full rack, another
terminal or device can be configured for the unused modules. For
example:
Parameter MessageView 421 Other Rack Device
Rack Number 1 1
Starting Module Group 0 6
Rack Size 3 /
4
1 /
4
Last Chassis? No Yes
Important: Two I/O systems can not share the same module.
The maximum rack number that can be assigned to the terminal
depends on the type of logic controller.