Rockwell Automation 6008-SV2R VMEbus remote I/O Scanner - Manual (Page 174)

Chapter
Programming the Scanner
8
8Ć40
Use the remaining input words and output words to move data between the
scanner and the PLC-5 processor. If you need to transfer more than 7
words, use a block-transfer, which can transfer up to 64 words of data.
BlockĆTransfer
Adapter-mode block-transfers are essentially continuous. As soon as a
transfer is completed, another block-transfer is queued immediately in the
PLC-5 processor; the processor then waits (with a buffered snap-shot of
the data) for the scanner to perform another block-transfer request. The
data that is transferred after the request is data from the previous
block-transfer. For example, if the scanner performs a block-transfer
request from the adapter-more processor every 500 msec, the data is at
least 500 msec old.
The scanner controls the actual communication transmission of the
block-transfer request. The adapter-mode processor controls the:
actual number of words of data that is transferred
location from which the data is transferred
Do not use ladder-logic block-transfer instructions for the adapter-mode
processor. You configure the block-transfers when you configure the
adapter channel.
Important: Adapter-mode block-transfer reads and writes in the same
group/module location must have the same length.
Affects of block-transfers on direct transfers
You can have as many as 15 writes and 15 reads. Each block-transfer to a
particular group/module location uses the I/O addresses for that rack/group
for status bits. These locations are lost to direct transfer. Therefore, if you
configure all available 15 block-transfer read/write pairs, no bits will be
available for direct transfer.
Do not program a block-transfer to group 0, module 1 because this area of
the direct transfer configuration file is used for communication status
exchanges between the scanner and the adapter-mode processor. Design Tip