Rockwell Automation 1794-ASB/E Remote I/O Adapter Module User Manual - Manual (Page 50)

3–16 Communicating with FLEX I/O Modules
Publication 1794ĆUM009D-EN-P - April 2004
After the rack size has been determined by the remote I/O adapter,
the data from the modules must be mapped into the data tables. Data
associated with digital modules is mapped into the input and output
image table.
Data transfer to and from the remote I/O adapter and digital modules
occurs every flexbus scan. This data is mapped into the input/output
image table.
IMPORTANT
The switch settings on the adapter module
determine whether both the input and output bits
are transferred. Standard addressing is the only
mode that maps both input and output bits for
each module.
For analog modules, only the MSB and MCB block transfer bytes
are mapped into the input and output image table. The remote I/O
adapter transfers data to analog I/O modules (block transfer write)
and from analog I/O modules (block transfer read) using BTW and
BTR instructions in your ladder diagram program. This data is
mapped to the data files selected in the ladder logic block transfer
instructions.
The adapter identifies the type of module in each base unit when the
module is added, and stores this information for later use, if
necessary.
IMPORTANT
If you are changing your configuration, you
must power down, then power back up after
changing a module type in a terminal base unit.
ATTENTION
!
In Standard Addressing Mode, FLEX I/O modules
do not support complementary I/O. Do not
attempt to use the complementary image table
word of a module in Standard Addressing Mode.
The complementary word is reserved for use by
the module.
After the remote I/O adapter has identified the modules present in its
system, it creates a “rack image” so data transfer can take place using
the remote I/O protocol.
Building a rack image consists of:
•
mapping each module to an I/O group (16 bits of input and 16
bits of output)
•
determining rack size – all empty terminal bases are counted
unless they occur at the end of the rack
•
automatically sizing the rack image, based upon the mode switch
setting
Mapping Data into the
Image Tables
Determining Rack Size