P74x/EN FD/N
1, P742, P743
(FD) 9-
3.1 Real-time operating system
• Real-time operating system for main board: the real-time operating system is used to
schedule the processing of the tasks to ensure that they are processed in the time
available and in the desired order of priority. The operating system is also responsible in
part for controlling the communication between the software tasks through the use of
operating system messages.
• Sequencer for coprocessor and communication boards: the sequencer executed all
functions at fixed frequency depending of the priority of the functions. The highest
frequency, 2400Hz, is the frequency of sample acquisition, signal processing and trip
decision. To start analogue acquisition at the same time on all peripheral units, the
sequencers of all peripheral units and central unit are synchronized and control the
analogue acquisition interfacing with system services software.
The software is split into tasks; the real-time operating system is used to schedule the
processing of the tasks to ensure that they are processed in the time available and in the
desired order of priority. The operating system is also responsible in part for controlling the
communication between the software tasks through the use of operating system messages.
3.2 System services software
As shown in Figure 4, the system services software provides the interface between the
relay’s hardware and the higher-level functionality of the platform software and the protection
& control software. For example, the system services software provides drivers for items
such as the LCD display, the keypad and the remote communication ports, and controls the
boot of the processor and downloading of the processor code into SRAM from flash EPROM
at power up.
3.3 Communication software
In accordance with sequencer used in coprocessor board, the communication software
sends frames at fixed frequency equal to 2400Hz. Likewise the contents of the frames is
independent of the frequency and of the status of the protections. The frames are split in
fixed parts according to the priority of each application. For example trip order and current
sample are respectively transmitted at 2400Hz and 1200Hz whereas the internal courier
communication or date & time are exchange at low frequency.
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