ProSoft Technology 5210-DFNT-RIO - Manual (Page 28)

RIO ♦ ProLinx Gateway Ladder Programming for RIO Module
Rockwell Automation® Remote I/O Adapter Driver Manual
Page 28 of 39
ProSoft Technology, Inc.
February 4, 2010
Therefore, the first word of data received in block 0 should be stored at data word
offset 0. The first word of data received in block 1 should be stored at data word
offset 60.
The next word in the header represents the BTW block identification code the
module is requesting from the PLC. The BTW logic should handle all blocks
requested by the module. This word should be copied to the first word of the
BTW block to be transferred next. Refer to the BTW Rung section below for a
discussion of how this word should be handled in the logic.
The last word of header information defines the number of valid words of data in
the block. The simplest way to handle the ladder logic is to configure the data
read area to be an even multiple of 60 words. This prevents the ladder logic from
having to handle short block messages. The BTR operations that interface with
the RIO module always transfer the same block sizes, therefore, there is no
optimization by setting the data area to a smaller size. In fact, the added code in
the ladder logic may slow the data transfer operation.
The data area follows the header section.This is the portion of the data block that
must be transferred to the user defined data table. The user is responsible for
setting up data tables and ladder logic to handle the BTR blocks. An example of
ladder logic to process four BTR blocks is displayed below: