Rockwell Automation 6008-SI IBM PC I/O SCNNR 6008-SI - Manual (Page 104)

Chapter 8
Block Transfer
8-14
The PLC5 has switches on it that determine the rack number it will
emulate while in adapter mode. The rack number can be any number
between 0–7. This will be the rack address the scanner uses to transfer
data to the PLC5. When the scanner does an autoconfigure, this will be the
rack number that is put into the scanner’s scan list.
Discrete Transfer
When both the scanner and the PLC5 are in run mode, 8 input words and 8
output words will automatically be exchanged between the scanner’s image
tables and rack 3 of the PLC5. The 8 words of the scanner’s input image
will be updated with the 8 words from the PLC5’s output image table from
rack 3. Likewise, the data from the scanner’s output image table
associated with the PLC5’s rack number will be transferred to the PLC5’s
rack 3 input image table. This happens automatically when the scanner is
in run mode, just like it transfers data to other full 16–slot I/O racks. There
is nothing that has to be programmed in ladder logic of the PLC5 to make
this happen. If the PLC5 wants the data from the scanner to go to its own
local I/O, the PLC5 will have to have a ladder logic instruction (file copy)
to get the data from rack 3 to rack 0.
Note: Of the 8 words that are transferred back and forth between the
scanner and PLC5, the first word, both from the input image and output
image table, is reserved for rack status information and block transfer
status. No data should be placed there by an application program.
Because the first word is automatically used for status, there are 7 words,
both input and output, that can be used to move data between the scanner
and the PLC5. If your application requires more than 7 words to be
transferred between the scanner and the PLC5, then the block transfer
protocol is used to transfer up to 64 words of data.