Rockwell Automation 1791-XXXX Discrete I/O AC and DC Block I/O Input and Output Modules - Manual (Page 10)

Introducing Block I/O
Chapter 1
1-3
Terminal Strip - Remote I/O link, power and input/output connections are
made to the removable terminal strip for easy connection of wiring, and
block replacement if necessary.
Switch Assembly - Two switch assemblies are provided for setting the I/O
rack number, starting I/O group, communication rate, last chassis, and
last state.
Status Indicators - Indicators display the status of communication and
input/output. Use these indicators to help in troubleshooting.
Block I/O is a complete I/O interface that includes the functionality of the
I/O rack, adapter, power supply, and I/O modules in a single unit. Connect
sensors and actuators to the module and use the remote I/O cable to
connect the block I/O to your programmable controller.
Connect the block I/O to your remote I/O link as you would any other
device (Figure 1.2). The block looks like a 1/4 I/O rack to the processor,
and uses two words of input image table memory and two words of output
image table memory. The block is addressed directly on the remote
I/O link.
Input and output data is scanned asynchronously and transferred back and
forth between the block and the controller input and output image table.
Figure 1.2
Block I/O Connection in a PLC System
Blocks are daisyĆchained to
a programmable controller or a
scanner
Block I/O Ć each block
is 1/4 I/O rack
Programmable Controller or
Scanner
10828ĆI
How Block I/O Fits in a
PLC System