Rockwell Automation 1791-IOBB USER MANUAL - Manual (Page 9)

Introducing Block I/O
Chapter 2
2Ć2
Wiring Connectors – The remote I/O link connector and input/output
connector are removable for easy connection of wiring.
Switch Assemblies – Two DIP switches are provided for setting the I/O
rack number, starting I/O group, transmission rate, last chassis, last state
and DH–485 terminator.
Status Indicators – LED indicators are provided for communication,
power and input/output status. These provide a visual indication for aid in
troubleshooting.
DH–485 Port – A plug–in port is provided for use with DH–485 data link
when used with the SLC controller.
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. Simply
connect sensors and actuators to the module and use the remote I/O cable
to connect the block I/O to your programmable controller (Figure 2.4).
The block uses sinking inputs and sourcing outputs.
In sinking inputs(Figure 2.2), the dc common is bussed on the block. and
the current is sourced from the field device. The sourcing field device
switches the hot side of the power supply bus causing current to flow
through the sourcing device to the sinking input on the block.
Figure 2.2
Sinking Input Example
DC Power
Supply
Field
Device
Field
Device
Sinking
Input
COM
+V
-V
10826-I
Block I/O
Input Common (COM)
Sourcing outputs(Figure 2.3) have the power bussed in the block. When
the output is on, current is supplied to the field control device, which sinks
the current. The field circuit and the equipment remain at ground potential
until the output is turned on.
How Block I/O Fits in a PLC
System