Embedded System QA II

Embedded system Q and A

1. what is difference between microprocessor and microcontroller?

microprocessor microcontroller
The microprocessor is having less in built memory and no inbuilt peripherals like ADC, SPI, IIC, UART, etc. The microcontroller is having more memory and inbuilt peripherals like ADC, IIC, SPI, UART.
The microcontroller is used to build embedded system with less external interfaces. The microprocessor is used to build general purpose computer.
The microcontroller cost is less. The microprocessor cost is more.
Microcontroller having less instructions and more bit handling instructions. Microprocessor having more instructions and few bit handling instructions.

2. what is clock cycle?
Clock cycle is the time duration between two clock pulses of an oscillator. The speed of a controller is more if number	of clock cycles per second is more. Microcontroller speed is measured using number instructions executes per second.

3. How to calculate the clock frequency of a contoller?
It is the frequency of the oscillator we are using to generate clock is the clock frequency of the controller. 

4. what is oscillator?
Oscillator is a circuit which produces the continuous alternating waveform without any input. Crystal osillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal to create an electric signal with a precise frequency.

5. What is the difference between serial and parallel communication?

In Serial communication data is transmitted serially bit by bit. In parallel communication data is transmitted parallely all the bits in one time.Serial communication needs less number of wires for connection. Parallel communication needs more wires for connection.

6. what is difference between rs232 and rs485?

RS232 RS485
The cable length limited to lesser than 50 feets. It is supporting long distance similar to rs422.
RS232 is single ended susceptible to noise since transmit and receive lines sharing the same ground. it supports multiple command and multiple listening devices and rs422 supports single command and multiple listeners.
Not multidrop - you can connect one rs232 device per port. if we want to connect to 3 meters to a pc we need rs232 protocol ports. rs485 uses 2 wires, twiested interface
Ground is common between tx and rx device, Need minimum 3 wire to communicate since the communication is happened in the two wires, you need to disable and enable the transmitter at the correct time. so that the proper communication should happen.

7. what is the difference between RISC and CISC controllers?
Reduced instruction set computer is having less number of instructions. The RISC processors have simple instructions taking about one clock cycle. the cisc processor has complex instructions that take 2 to 15 clock cycles.
Performance is more focussed on software. Performance is more focused on hardware.
Most instrcutions are completed in 1 machine cycle. It has a memory unit to implement complex instructions.
- pipelining technique used to speed up RISC controllers. - multiple register set. - ecxecution time is very less - code expansion can be a problem - instruction decoding is simple - It does not require external memory for calculation - The most common risc processors are Alpha, ARC, AVR, MIPS, PA-RISC, Power Architecture, SPARC - RISC architecture is used in high end applications such as vedio processing, telecommunications and image processing. - it is having single register set - ecxecution time is very high - code expansion is not aproblem. - instruction decoding is complex - It requires external memory for calculation - examples of CISC processors are the System/360, VAX, PDP-11, Motorola 68000 family, AMD and Intelx86 CPU. - CISC architecture is used in low-end applications such a security system, home automation.

8. mention the required components of embedded system?

- Hardware -
  - microcontrollers
  - memory
  - timers
  - IO circuits
  - system application circuits, 
  - software
  -It checks the availabity of system memory
  - It checks the processor speed availability 
  - the need to limit the power lost when running the system continuously
It runs the processor as per scheduling and do the switching from one process to another

9. what are realtime embedded system?
Real time embedded system are systems that monitor, respond or control an external environment. This environment is connected to the system through actuators, sensors and input output interfaces.

10. what is Watchdog timer?
Watchdog timer will reset the system if it is not reloaded before watchdog timer expires. If the system do some malfunction then it would not reset the timer so the watchdog timer will reset the system.