Rockwell Automation 1747-DSN DISTRIBUTED I/O SCANNER - Manual (Page 9)

Chapter 1
Introduction
1–2
The DIO Link is an Allen–Bradley communications network supporting high
speed transfer of control information. A DIO Link consists of a single
master device (the scanner) and multiple slave devices (the I/O blocks). The
scanner and I/O blocks are daisy chained together by a single twisted pair
cable (Belden 9463).
Each I/O block is assigned a I/O block number from 1 to 31 (excluding 16,
which is invalid) by setting the appropriate dip switches on the I/O block.
I/O block numbers must be assigned consecutively. For example, if 5 I/O
blocks are used, they must be assigned I/O block numbers 1 to 5. I/O blocks
do not have to be wired in a contiguous order. For example, I/O block 5 can
follow I/O block 2.
The inputs and outputs for each I/O block are mapped into the words in the
SLC processor’s input and output images. These words correspond to the
scanner’s slot number and the I/O block’s number. For example, if the
scanner is installed in slot 2 of the SLC Rack, I/O block number 1 will have:
•
its input data reflected in word 1 of the slot 2 input image
•
its output data reflected in word 1 of the slot 2 output image.
The scanner communicates with each I/O block in a round robin fashion.
The scanner initiates communications with an I/O block by first sending its
output data. The I/O block then responds by sending its input data back to
the scanner. After the scanner completes its I/O transfer with the last I/O
block, it begins another transfer with the first I/O block.
The DH–485 Data Link is an Allen–Bradley communications network that
supports the transfer of information between programming devices and SLC
processors. The programming device and SLC processor are attached to the
DH–485 Data Link using either an Isolated Coupler or an I/O block. The
DH–485 Data Link may consist of multiple Isolated Couplers and/or I/O
blocks that provide for communication between several programming
devices and/or processors.
The Isolated Couplers and I/O blocks are daisy chained together by a single
twisted pair cable (Belden 9842) to form the DH–485 Data Link. The
programming devices and SLC processors are attached to the Isolated
Coupler or I/O block using Communication Cables (Catalog Numbers
1747–C10 and –C11).
For additional information on the DH–485 Data Link, see the Installation and
Operation Manual for SLC 500 Modular Hardware Style Programmable
Controllers, Publication 1747–804.
DIO Link Overview
DH–485 Data Link Overview