What are the different types of system involved in embedded system?
Embedded systems are used to give the response in real time. So, it consists of
the real time systems that allow the correct information to be passed to get
the correct responses. For example, it includes of the flight control system
that produce the responses in real time and it always the take the values also
in real time. If any delay been caused by the system then it deals in the fatal
error. The real time system includes the system that provides the response on
time with the small delay. Real time systems include of many other system such
as:
- Hard Real-Time Systems - these are the systems that server the purpose
of having constraints that are hard and it totally depends on the time to
provide the response on time.
- Soft Real-Time Systems - these systems serves the purpose of having few
delays in giving up the responses that can tolerate small variations.
- Hybrid Real-Time Systems - these systems includes the properties from
both the systems and increases the performance.
What are the different types of Buses used by the embedded systems?
The buses are used to pass the messages between different components of the
system. There are buses existing as:
• Memory Bus: it is related to the processor that is connected to the memory
(RAM) using the data bus. This bus includes the collection of wires that are in
series and runs parallel to each other to send the data from memory to the
processor and vice versa.
• Multiplexed Address/Data Bus: Multiplex data bus consists of the bus that can
read and write in the memory but it decreases the performance due to the time
consumed in reading and writing of the data in the memory.
• De-multiplexed Bus: these consists of two wires in the same bus, where one
wire consists of the address that need to be passed and the other one consists
of the data that need to be passed from one to another. This is a faster method
compared to other.
• Input/Output bus: it uses the multiplexing techniques to multiplex the same
bus input and output signals. This creates the problem of having the deadlock
due to slow processing of it.
What is the main function of Multiplexed Address/Data Bus?
The memory bus is used to carry the address and the data from the processor to
the memory so that it can be easily accessed by the devices. These buses carry
the value of the data that has to be passed for the proper functioning. The use
of the technique “Time division multiplexing” is used that allow the reading
and writing of the data to be done from the same bus line. This requires lots
of time to be given to the bus so that it can complete the read and write
operation of the data in the memory. This is very expensive process due to the
data transfer technique that is used in between the processor and the memory.
This also gives the concept of cache and provides algorithms to solve the
problems occurring in read and writes operations.
How does Input/Output bus functions?
Input and output devices or functions allow the user to interact with the
external files. Input and output functions are used to transfer the load on the
bus. It uses the multiplexes having the input and output signals that remain
same. Input and output buses move at the slower rate or speed than the
processor speed. This increases the problem of bottleneck or the deadlock due
to poor performance. There is a possibility to send more transistors for a
layout to be given. These different devices may have very different speeds of
communication. When programming IO bus control, make sure to take this into
account.
In some systems, memory mapped IO is used. In this scheme, the hardware reads
its IO from predefined memory addresses instead of over a special bus. This
means you'll have simpler software, but it also means main memory will get more
access requests.
What is the function of simple thread poll in embedded system?
Simple thread poll allow the ready output to be passed for checking by giving it
to the bus that is free and then the output is sent along the thread. The bus
can send the output depending on the time that has been given and during the
transfer the user won’t be able to perform any other operation. The input is
given after finding out the bus is free or not and if it free then a check is
made to see that the input exists or not. This thread poll is easy to
understand but it is not efficient method to allow the data to be put over the
bus manually. The problem of not doing multi-tasking can occur due to doing one
task at a time. The method is only be used when input/output occurs at interval
that are infrequent.
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