Memory
Limitations
16
Megabytes of RAM and a Flash file system with 16 Megabytes is abundant
for most SCADA, control or instrumentation applications. (Consider
the meager memory in the controller the IPm is probably replacing.)
The LINUX kernel, all IPm firmware,
and typical configuration files will use less than half of the Flash
memory. Additional memory (64 Meg of RAM and 128 Megabytes of Flash)
is available in the
SixTRAK IPm (part number ST-IPM-6350). When planning your applications,
just remember that IPm is an embedded controller, not a main frame
computer. Processor
Speed / Capabilities Limitations
There
are really no significant limitations to the computing possibilities
of an IPm controller
or RTU. It will run any LINUX application designed for use
on an embedded controller (no operator interface – see below).
The PowerPC has the equivalent processing power of a low-end Pentium
processor. This is a GREAT amount of power for a process controller!
For reference, it runs ISaGRAF
programs approximately ten times faster than the legacy VersaTRAK
RTU or SixTRAK Gateway that it replaces.
Response
Time Limitations
An
IPm controller
or RTU is recommended for applications requiring an overall
response time (deterministic performance) of 20 milliseconds or
more. This conservative and practical advice is based upon the
fact that some LINUX software may not perform adequately with
a time slice of less than 10 milliseconds (the default IPm setting).
Of course, if you add real-time extensions to the system, an IPm
controller can be run faster in custom applications.
The IPm concept
is not to run microsecond applications, but rather to continue
to provide responsive performance (not slow down) as your applications
grow. In other words, to use the PowerPC to make big applications
run as well as small applications – the SIXNET SCS (scalable)
concept is a practical advantage.
Adding
a Display to an IPm Controller or RTU
The
remarkable performance of an IPm
controller or RTU is attributable in part to the fact that
it is not burdened by a built-in or dedicated graphical interface.
Thus, it boots in a few seconds and is always available to run
its real-time tasks. (An ISaGRAF
program uses only a few percent of the processing power that a
graphical interface would use.) The alternative is to use any
one of the multitude of great industrial display products on the
market. (We have seen a IP67 rated display with an Ethernet port
for only $250.) Many of these displays use Modbus to communicate
and they are completely configurable, meaning that no programming
is required in the IPm to use them. All operator interfaces tested
to work with a VersaTRAK RTU may be interfaced to an IPM controller
or RTU. Of course you may use the LINUX programming capabilities
of IPm to interface to any display with any serial interface.
The sky is the limit.
Select any display product you like. |
