Publication 1734-UM002C-EN-P - July 2003
Using Auto Start Mode 3-3
When the Adapter Uses Auto Start Mode, How Does it Map
I/O Data?
In Auto Start Mode, you can map I/O data in the adapter’s memory in
one of the following ways:
• Byte Boundaries
• Word Boundaries
• Double Word Boundaries
• Fixed Boundaries
Byte Boundaries
Each node’s I/O data is mapped in the adapter’s memory at the next
available byte. This option works best in applications that use
Allen-Bradley PLCs and SLCs.
Word Boundaries
Each node’s I/O data is mapped in the adapter’s memory at the next
available word. This option works best in applications that use
Allen-Bradley PLCs and SLCs.
Double Word Boundaries
Each node’s I/O data is mapped in the adapter’s memory at the next
available double word. This option works best in applications that use
Allen-Bradley Logix products.
Fixed Boundaries
The map to the fixed location is based on the node address. Mapping
size ranges from 1 to 32 and is set using an EDS parameter. The
mapping for a node with address 1 begins on byte 2. The formula for
mapping is: 2+((N-1)(mapsize)), where N = node address.
• The user specifies fixed map size using EDS parameters
• Data mapped after status/channel words in I/O image,
beginning with byte 2
• No data area reserved for MAC ID 0 (the adapter)
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