ControlLogix DeviceNet Scanner Module 21
Publication 1756-IN566B-EN-P - April 2001
ControlLogix Controller Interface
The 1756-DNB module supports several different size input, output,
and status structures over the ControlLogix backplane. These I/O
structures were created to reduce the complexity of connecting
DeviceNet I/O and status data with ladder programs. The module
creates all 3 structures whether or not DeviceNet nodes are
configured or online. The RSLogix 5000 software directs the controller
to connect to these predefined default I/O structures. The controller
automatically performs periodic updates of the structures on a cyclic
basis.
The RSNetWorx for DeviceNet software configures scanlist map
segments that are used to copy specific portions of I/O data between
the I/O structures and DeviceNet network packets.
Output Structure
The controller controls output I/O by writing output data to an
output structure in the 1756-DNB module. The scanner module then
delivers a copy of these output values to modules on DeviceNet. The
output structure consists of a 32-bit command register and a variable
size 32-bit array of up to 123 words for output data.
IMPORTANT
The 1756-DNB scanner supports ControlLogix
connections with only one controller at a time.
Output Structure Element Description Data Type
module command register This 32-bit register consists of
several bits that affect the module’s
behavior on the network.
1 x 32-bit register
output_data 123 x 32-bit data array
Allen-Bradley
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