Rockwell Automation 1738-ADNX ArmorPoint I/O DeviceNet Adapters - Manual (Page 36)

Publication 1738-UM001A-EN-P - February 2005
2-20 What Is the ArmorPoint DeviceNet Adapter?
The four data transfers are not necessarily sequential. Transfers 2 and
3 typically occur more frequently than transfers 1 and 4.
Image Table Mapping
Your adapter receives data from:
• master devices (e.g., scanners) - output data is then passed to
ArmorPoint I/O modules
• input modules - input data is passed to the scanner
The adapter must map the data it receives to its internal memory
before passing it to the appropriate device. The I/O map for a module
is divided into:
• read bytes - input and status bytes
• write bytes - output and configuration bytes
The data is mapped by 3 buffers for input data (each representing an
I/O connection on the primary DeviceNet) and 1 buffer for output
data (representing data sent for Poll or COS connections on the
primary DeviceNet).
The number of read bytes or write bytes can be 2 or more. The length
of each I/O module's read bytes and write bytes vary in size
depending on module complexity. Each I/O module supports at least
1 input byte or 1 output byte. Status and configuration are optional,
depending on the module.