Rockwell Automation T8110B/T8110 Trusted TMR Processor - Manual (Page 31)

Trusted
TM
TMR Processor T8110B/T8110
Issue 18 Feb 08 PD-T8110B/T8110 31
4.8. Composite Scan Time Estimation (from TÜV release 3.5)
The composite scan time for a Trusted TM system represents the time required to read the input data,
solve the application logic, and write the output data. This sequence is repeated cyclically for as long
as the Trusted
TM system is executing an application. For convenience, the above cyclical sequence is
broken down into four discrete elements: input modules, output modules, application and
communications. The estimated composite scan time is the sum of those four elements.
The calculations here apply to systems from TÜV release 3.5. For systems before release 3.5, refer to
section 4.7.
4.8.1. Input modules
The Input Module time is based on the number of Trusted TM High Density Input modules. The time
calculations are independent of the number of channels on each module (i.e. a 60 channel DUAL
module has an equivalent input module time as a 40 channel TMR module). The Input Module time is
calculated by multiplying a time factor by the total number of High Density Input modules. Digital and
analogue modules have the same time factor.
The input module time may be reduced by setting individual modules to scheduled polling in their entry
in the System.INI configuration. As an approximation, this will reduce their scan time effect in
proportion to their poll interval.
Factor No. Input Modules Input Total
4.5 ms x
4.8.2. Output Modules
The Output Module time is based on the number of Trusted TM High Density Output modules. The time
calculations are independent of the number of channels on each module (i.e. a 32 channel 120Vdc
Digital Output module has an equivalent output module scan time as a 40 channel Analogue Output
module). The Output Module time is calculated by multiplying a time factor by the total number of High
Density Output modules.
The output module time may be reduced by setting individual modules to scheduled polling in their
entry in the System.INI configuration. This spaces out the read operations from the module. As an
approximation, this will reduce two-thirds of their scan time effect in proportion to their poll interval. The
remaining time is due to write operations to the module. Selecting ‘write by exception’ in the entry in the
System.INI configuration will prevent write operations if the outputs have not changed.
Scan Factor No. Output Modules Output Total
7 ms x