Example Discrete I/O Throughput With Block Transfers Present - Allen-Bradley 1747-SN User Manual

A–8 Specifications
Publication 1747 6.6 - July 1996

Example Discrete I/O Throughput with Block Transfers Present

An SLC 5/03 is using a scanner to control a 115.2K baud RIO link
that has 3 adapters and 4 logical devices.
Adapter #1 (1747-ASB module):
starting logical rack 0, logical group 0
12 logical groups (1 1/2 logical racks)
one 8 word and two 4 word BT write/read modules in logical rack 0
one 2 word BT write/read module in logical rack 1
Adapter #2 (1771-ASB module):
starting logical rack 2, logical group 0
2 logical groups (1/4 logical rack)
one 64 word BT write/read module
Adapter #3 (1771-ASB module):
starting logical rack 2, logical group 2
2 logical groups (1/4 logical rack)
one 32 word BT write/read module
1. Use the throughput formula to calculate the maximum throughput
of the 1747-ASB module.
T = 2T + 2T
dm–bt ps RIO
T = 25.0 ms, which is from the APS reference manual (assume for
ps
example)
T = The total RIO scan time (ms)
RIO
T = Additional time due to sending any BT data on the RIO link
btx
T = Two 1747-ASB module backplane scan times (calculated from
adp
ASB
manual) = 2(4.5) = 9.0 ms
T = 22.0 ms from the table on page A–13, T
SNo–bt
Transfers
(Normal Mode). There are 3 logical racks configured.
T = 5.0 ms
SNi
T = 10.0 ms, which is from I/O module instruction sheets
id
T = 1.0 ms, which is from I/O module instruction sheets
od
T = 2(25.0) + 2T
dm–bt RIO
+ 2T + T + T + T
btx adp SNo–bt
+ 2T + 9.0 + 22.0 + 5.0 + 10.0 + 1.0
btx
+ T + T
SNi id od
with Block
SNo