Rockwell Automation 1769-ADN Compact I/O 1769-ADN DeviceNet Adapter - Manual (Page 25)

1 Publication 1769-UM001B-EN-P - October 2002
Chapter
2
How Communication Takes Place and I/O
Image Table Mapping
This chapter explains how communication takes place and about I/O
image table mapping. Included is information about:
• I/O Structure
• Communication Choices
• Mapping I/O Data into the Image Table
Communication Over the
1769 Bus One 1769-ADN DeviceNet adapter can interface with up to 30
Compact I/O modules to make a Compact I/O system. The adapter
communicates to other network system components (typically a
controller or scanner and/or programming terminals) over the
DeviceNet network.
The adapter communicates with its I/O modules over the 1769 bus.
The adapter and I/O modules also receive 5Vdc and 24V dc power
through the bus interface via a 1769 power supply. The 1769 bus and
all devices on the 1769 bus have system configuration limits. Refer to
Using Banks of I/O on page 3-7 for more information.
The I/O map for an I/O module is divided into input data words and
output data words. The number of input data words or output data
words can be 0 or more. The length of each I/O module’s input data
words or output data words vary in size, depending on the module’s
complexity. Each I/O module will support at least one input data
word or one output data word.
I/O Structure Output data is received by the adapter in the order of the installed I/O
modules. The output data for Slot 1 is received first, followed by the
output data for Slot 2, and so on up to Slot 30.
The amount of output data in the adapter’s output image for each I/O
module is based on the configuration of each I/O module done as
part of the 1769-ADN configuration. If an I/O module is configured to
have 0 words of output data, then it does not appear in the output
image of the 1769-ADN. Only a module’s output data can be in the
1769-ADN output image - a module’s configuration data cannot.
The first two words of input data sent by the adapter are the Adapter
Status Words. This is followed by the input data from each slot, in the
order of the installed I/O modules. The input data from Slot 1 is first
after the status words, followed by Input data from Slot 2, and so on
up to Slot 30.