Rockwell Automation Publication ICSTT-RM447M-EN-P - July 2019 53
Chapter 3
Controller Functionality
This chapter describes the controller functions that give you the flexibility to
create a system to meet your specific business needs.
Field Data Handling
The AADvance controller is a logic solver and I/O processing device. The field
data and field element control commands are routed across the field wiring to
the termination assemblies which are uniquely matched to their respective I/O
modules. An internal bus structure and a secure communication protocol
transport the data and command signals to and from the processing software.
The processor has a SIL 3 rated operating system and runs user developed
applications to analyze and respond to the field data and produce the necessary
field commands and user information. These application programs, developed
by the user to meet their safety and business requirements are downloaded
from a Workstation that has the AADvance Workbench application
development software installed. A security device on the processor backplane
helps prevent unauthorized access to the application software.
Process Safety Time
The Process Safety Time (PST) setting defines the maximum time that the
processor will let the outputs stay in the ON state if certain internal diagnostic
faults or systematic application faults occur. If the process safety time expires
the controller will go to its "safe state". The PST must be specified for the whole
controller, this is a top level setting that you make once for the whole controller
and is set at the processor module. I/O modules can be set at a lower PST but
must not go over this overall setting.
An AADvance controller adopts a default value for the PST = 2500 ms which
can be adjusted to meet your system requirements by using the following
simple equation:
where PSTeuc is the process safety time for the equipment under control.
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