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P24xM
3
SYSTEM LEVEL SOFTWARE
3.1
REAL TIME OPERATING SYSTEM
The real-time operating system is used to schedule the processing of the various tasks. This ensures that they are
processed in the time available and in the desired order of priority. The operating system also plays a part in
controlling the communication between the software tasks.
3.2
SYSTEM SERVICES SOFTWARE
The system services software provides the layer between the hardware and the higher-level functionality of the
platform software and the protection and control software. For example, the system services software provides
drivers for items such as the LCD display, the keypad and the remote communication ports. It also controls things
like the booting of the processor and the downloading of the processor code into RAM at startup.
3.3
SELF-DIAGNOSTIC SOFTWARE
The device includes several self-monitoring functions to check the operation of its hardware and software while in
service. If there is a problem with the hardware or software, it should be able to detect and report the problem, and
attempt to resolve the problem by performing a reboot. In this case, the device would be out of service for a short
time, during which the 'Healthy' LED on the front of the device is switched OFF and the watchdog contact at the
rear is ON. If the restart fails to resolve the problem, the unit takes itself permanently out of service; the 'Healthy'
LED stays OFF and watchdog contact stays ON.
If a problem is detected by the self-monitoring functions, the device attempts to store a maintenance record to
allow the nature of the problem to be communicated to the user.
The self-monitoring is implemented in two stages: firstly a thorough diagnostic check which is performed on boot-
up, and secondly a continuous self-checking operation, which checks the operation of the critical functions whilst
it is in service.
3.4
STARTUP SELF-TESTING
The self-testing takes a few seconds to complete, during which time the IED's measurement, recording, control,
and protection functions are unavailable. On a successful start-up and self-test, the 'health-state' LED on the front
of the unit is switched on. If a problem is detected during the start-up testing, the device remains out of service
until it is manually restored to working order.
The operations that are performed at start-up are:
1.
System boot
2.
System software initialisation
3.
Platform software initialisation and monitoring
3.4.1
SYSTEM BOOT
The integrity of the Flash memory is verified using a checksum before the program code and stored data is loaded
into RAM for execution by the processor. When the loading has been completed, the data held in RAM is compared
to that held in the Flash memory to ensure that no errors have occurred in the data transfer and that the two are
the same. The entry point of the software code in RAM is then called. This is the IED's initialisation code.
P24xM-TM-EN-2.1
Chapter 4 - Software Design
47
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Table of Contents
Troubleshooting
