Rockwell Automation 1747-BSN Backup Scanner Module - Manual (Page 58)

Publication 1747-UM010B-EN-P - September 2003
4-6 Operating Your SLC 500 Backup System
The figure below shows how the programming device sees the
secondary processor which is not physically connected to the DH+
link.
Data Table Transfer Each 1747-BSN module is capable of transferring up to 2 KWord of the
SLC 5/0x data table. This capacity is increased as the number of
1747-BSN modules per chassis is increased in a redundant system. For
example, a system with eight 1747-BSN’s in each chassis is capable of
transferring up to 16 KWord of synchronizing data table information.
The 2 KWord that can be transferred by a single module is divided
into 16 blocks of 128 words (that is equal to the maximum length of a
COP instruction). The address space M0:s.3500 through M0:s.5547 is
used by the primary SLC 5/0x to send the data. The address space
M1:s.3500 through M1:s.5547 is used by the secondary SLC 5/0x to
read the data from the secondary 1747-BSN. In addition, the address
spaces M0:s.3400 through M0:s.3499; and M1:s.3400 through
M1:s.3499 are used for status and control exchange between the
SLC 5/0x and the 1747-BSN.
IMPORTANT
The DH+ connection to the secondary processor is
meant for remote programming only. Also, only one
terminal at a time may connect to the secondary
processor. No DH+ messages can be sent to or from
the secondary processor.
SLC500 BSN BSN SLC500
Programming Device
DH+
HSSL
Node address = n Node address = n +1