Rockwell Automation 1747-BSN Backup Scanner Module User Manual
Page 177
Publication 1747-UM010B-EN-P - September 2003
Specifications A-13
Substitute values for the variables in the formulas above. Locate these
values in the following documents:
Variable
Variable Description
Location of Variable
T
M0
Time to perform M0 file write to enable BT
Appendix B
T
SNo-bt
Backup Scanner Output Delay time with BTs
present. There must be an output delay time
added for each BT buffer that is being used since
the backup scanner processes only one BT
enable or disable every T
SNo-bt
(to minimize the
impact on discrete I/O throughput).
(1)
(1) When calculating BT throughput, one T
SNo-bt
is also required to handle the BT response.
see the section
Determining T
SNo-bt
on
T
btwait
Equals the sum of the throughput times for all
BTs scheduled to the same logical rack (time
waiting is queue), + T
SNo-bt
(time to schedule
pending BT). If multiple BTs are not being
performed to the same logical rack, this value
equals zero.
calculated
T
RIO
RIO scan time without BTs
see the section RIO Scan
Time Calculation (T
RIO
)
on
T
btx
Amount that the RIO scan time can be increased
due to BTs. This includes the time for the backup
scanner to initiate the BT and transfer the data.
see the section
Determining T
btx
on page
A-8
T
adp-bt
Time for the adapter to acknowledge the BT
request. For the 1747-ASB, the manual defines
this as no more than one (ASB) backplane scan
time and two RIO scans. However, the two RIO
scans are already included in the above equation
so only the ASB scan time needs to be added.
adapter user manual
T
ps
One processor scan time may occur before the
SLC control program detects that the DN flag has
been set or cleared
measured or estimated