Installation guide

178 Modbus Plus Transaction Elements
890 USE 100 00
A .1 Transaction T iming Elements
A .1.1 Token Holding Time
Eachnode holds the networktoken for a minimumlength of time ifit
has notransactions. The minimum token time is approximately 530
microseconds. The token will be held for a longer time depending upon
the quantity and size of pending transactions.
Typical times are shown in the charts below. Each chart shows the
types of transactions the device can handle, how many concurrent
transactions are available, and the times required to process single and
multiple paths.Times are shownfor smallandlargesizes of
transactions. All times are in milliseconds.
A .1.2 W orst Case Timing Examples
Note that the token holding times shown in the right column are
worstcase times, with all of the device’s paths active, with all paths
moving the full amount of data, and with full queueing. With proper
design of your network these times should not occur in practice.
The only types of transactions that you should consider for calculating
the loading on a properlydesigned network are the Data Master paths
and Data Slave paths, with occasional queueing.
You should plan your network layout and application programming so
as to avoid the worstcase times. Use the formulas in Chapter 3 to
predict response times under various loading conditions. That chapter
also provides guidelines for designing your network so as to avoid or
minimize queueing in your application.
Controllers
Two Registers 100 Registers
Transaction
Type
Available
Transactions
One
Transaction
All
Transactions
One
Transaction
All
Transactions
MSTR DM path 4 1.4 5.6 3.0 12.0
DS path 4 1.4 5.6 3.0 12.0
Dequeue transaction
to slave path
4 1.4 5.6 3.0 12.0
PM path 1 1.4 1.4 3.0 3.0
PS path 1 1.4 1.4 3.0 3.0
Totals 8.4 21.0 18.0 45.0