Rockwell Automation 1747-BSN Backup Scanner Module - Manual (Page 102)

Publication 1747-UM010B-EN-P - September 2003
6-6 Module Control and Status Word
2. M1:s.3410: Data Transfer Status Word (DTSW)
This word is used in both the primary system and the secondary
system to affect the transfer of data on the HSSL.
•
Primary System - The word must be monitored by the primary
processor because this word is used by the primary 1747-BSN
to acknowledge that the 1747-BSN has received the data
block from the processor and is ready for the next transfer for
that particular data block number.
•
Secondary System - The word is used by the 1747-BSN to let
the processor know that a new data block is ready for transfer
from the secondary 1747-BSN to the secondary processor. The
ladder program in the secondary processor must monitor the
bits in this word to know when to copy new HSSL data from
the 1747-BSN to the processor data table.
3. M0:s.3411: Data Transfer Handshake Word (DTHW)
This word is used by the secondary processor to inform the
secondary 1747-BSN that it has received the latest data block
and is ready for the next transfer for that particular data block
number.
Data Transfer Control Word The Data Transfer Control Word (DTCW) is used to control the data
table transfer from primary to the secondary system. Each bit
corresponds to a block in the 1747-BSN module.
If the primary SLC 5/0x writes a new block into the primary 1747-BSN,
then one bit corresponding to this block must be set in the DTCW
word to advise the backup module that a new valid block is ready to
be transferred to the secondary SLC 5/0x. The figure below shows the
meaning of the bits in this word.