Allen-Bradley 1747-SN - Page 162

Specifications A–9
Publication 17476.6 - July 1996
2. Calculate the total RIO scan time (T
RIO
). Locate the baud rate
(115.2K) and adapter size which is found in the table on page
A–4. Multiply the RIO scan times listed under the 115.2K
heading by the number of each different type of rack that you
have. Add those number together.
T
RIO
= Tadapter1 + Tadapter2 + Tadapter3
T
RIO
= 1(5.5) + 1(4.0) + 2(3.5)
T
RIO
= 16.5 ms
3. Calculate the maximum T
ri
time for each logical rack. Do this by
determining the largest BT that will occur to any device within a
logical rack and calculating the transfer time using the table on
page A–7. 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