Rockwell Automation 1747-BSN Backup Scanner Module - Manual (Page 175)

Publication 1747-UM010B-EN-P - September 2003
Specifications A-11
3. Calculate the maximum T
ri
time for each logical rack. Do this by
determining the largest BT that occurs to any device within a
logical rack and calculating the transfer time using the table on
page A-8. Then add together the T
ri
times for each logical rack to
obtain T
btx
.
T
ri
for rack 0 = 0.150(8) + 3.5 = 4.7 ms (maximum BT to rack 0 is
8 words)
T
ri
for rack 1 = 0.150(2) + 3.5 = 3.8 ms (maximum BT to rack 1 is
2 words)
T
ri
for rack 2 = 0.150(64) + 3.5 = 13.1 ms (maximum BT to rack 2
is 64 words)
T
btx
= T
ri0
+ T
ri1
+ T
ri2
= 4.7 + 3.8 + 13.1 = 21.6 ms
4. Substitute all the values for variables in the throughput formula
and solve for throughput.
T
dm-bt
= 2(25.0) + 2(16.5) + 2(21.6) + 9.0 + 22.0 + 5.0 + 10.0 + 1.0
T
dm-bt
= 173.2 ms = maximum throughput
Block Transfer Throughput
Block transfer throughput is the time from when the BT is enabled via
the EN bit, until the DN bit is processed. The following BT timing
explanations are based on the directional continuous BT example
shown on page 7-19, where a BT is re-triggered automatically upon
each completion.