Rockwell Automation 1791-I0VW USER MANUAL - Manual (Page 10)

Introducing Block I/O
Chapter 1
1-5
Figure 1.4
Sourcing Input Example
Field
Device
Input
+V
10917ĆI
Block I/O
dc Power
Supply
dc Common Bus
ĆV
In sinking outputs (Figure 1.5), the current flow is reversed. The dc
common is bussed on the module and the current is sourced from the field
device being actuated. When an output is turned on, the output switch in
the module sinks the circuit, causing current to flow from the +V bus
through the field device to the module.
Figure 1.5
Sinking Output Example
dc Power
Supply
Field
Device
Field
Device
+V
ĆV
Bus
Common
Fuse
Fuse
10918ĆI
Block I/O
Block I/O functions exactly like any Allen-Bradley remote I/O product.
Input and output data is scanned asynchronously and transferred back and
forth between the block and the controller input and output image table.
You connect the block I/O to your remote I/O link as you would any other
device. The block looks like a 1/4 I/O rack to the processor, and uses 2
words of input image table memory and 2 words of output image table
memory. The block is addressed directly on the remote I/O link.