8251 USART interview questions and answers

  1. What is IC 8251?
  2. How many pins does IC 8251 have?
  3. What is USART?
  4. Why 8251 is called a USART?
  5. What is simplex half & full duplex modes of communication?
  6. What is the difference between asynchronous & synchronous mode of communication?
  7. Explain control word format of 8251?
  8. Define frame in asynchronous communication and draw it.
  9. Define baud rate.
  10. Define bit rate.
  11. Define mode word register of 8251 for asynchronous mode..
  12. Define mode word register of 8251 for sync mode..
  13. What is the significance of SYNC DETECT signal in 8251?
  14. What is the significance of BREAK DETECT signal in 8251?
  15. Define command word register of 8251.
  16. Define status word register of 8251.
  17. What are the applications of 8251?
  18. Whether write operation is possible with status word register?
  19. Whether operation read is possible with command word register?
  20. What is parity error in 8251?
  21. What is over run error in 8251?
  22. What is frame error in 8251?
  23. What is hunt mode in 8251?
  24. Explain block diagram IC 8251?
  25. Explain the logic of 8251 program.
  26. Explain the interfacing of 8251 with 8086.
This entry was posted in Hardware. Bookmark the permalink. Post a comment or leave a trackback: Trackback URL.

12 Comments on 8251 USART interview questions and answers

  1. athulya
    Posted 7/19/2007 at 6:19 am | Permalink

    frame error: indicates a missing stop bit. This error can only happen when the communication settings of transmitter and receiver (e.g. baud-rate) don’t match, when the connection was lost, or the transmitter is faulty

  2. athulya
    Posted 7/19/2007 at 6:20 am | Permalink

    ans 22:
    frame error: indicates a missing stop bit. This error can only happen when the communication settings of transmitter and receiver (e.g. baud-rate) don’t match, when the connection was lost, or the transmitter is faulty

  3. athulya
    Posted 7/19/2007 at 6:22 am | Permalink

    ans 21:
    overrun error: indicates that a new data character was received before the previously character was read by the host microprocessor. A data loss occured

  4. linu
    Posted 7/19/2007 at 6:24 am | Permalink

    ans 20:
    parity error: set when the parity of an incoming data character does not match the expected value.

  5. athulya
    Posted 7/19/2007 at 6:50 am | Permalink

    ans 10:In telecommunications and computing, bitrate (sometimes written bit rate, data rate or as a variable R or fb) is the number of bits that are conveyed or processed per unit of time. Bit rate is synonymous to data rate and digital bandwidth.

  6. athulya
    Posted 7/25/2007 at 1:54 am | Permalink

    ans 1:The 8251 is a USART (Universal Synchronous Asynchronous Receiver Transmitter) for serial data communication. As a peripheral device of a microcomputer system, the 8251 receives parallel data from the CPU and transmits serial data after conversion. This device also receives serial data from the outside and transmits parallel data to the CPU after conversion

  7. athulya
    Posted 7/25/2007 at 1:55 am | Permalink

    USART (Universal Synchronous Asynchronous Receiver Transmitter) for serial data communication. As a peripheral device of a microcomputer system, it receives parallel data from the CPU and transmits serial data after conversion. This device also receives serial data from the outside and transmits parallel data to the CPU after conversion

  8. shruti
    Posted 7/25/2007 at 1:56 am | Permalink

    ans 3:USART (Universal Synchronous Asynchronous Receiver Transmitter) for serial data communication. As a peripheral device of a microcomputer system, it receives parallel data from the CPU and transmits serial data after conversion. This device also receives serial data from the outside and transmits parallel data to the CPU after conversion

  9. shruti
    Posted 7/25/2007 at 3:15 am | Permalink

    ans 5:
    A simplex mode of communication is one where all signals can flow in only one direction.

    A half-duplex system provides for communication in both directions, but only one direction at a time (not simultaneously). Typically, once a party begins receiving a signal, it must wait for the transmitter to stop transmitting, before replying.

    A full-duplex system allows communication in both directions, and unlike half-duplex, allows this to happen simultaneously. Land-line telephone networks are full-duplex since they allow both callers to speak and be heard at the same time.

  10. shruti
    Posted 7/25/2007 at 3:47 am | Permalink

    ans 6:
    In synchronous communications the transmitter and receiver clock have to be exactly synchronized.
    Synchronous communications has constant bit rate.

    In asynchronous communications the transmitter and receiver clock do not have to be exactly synchronized.
    Asynchronous communications is variable bit rate.

  11. logamurthy
    Posted 9/4/2007 at 12:37 am | Permalink

    Ans 9:
    number of samples transmitted or processed per second is baud rate. for example at particular time number of cars(samples) passed on the road is baud rate.

  12. bharathkumar.s
    Posted 12/18/2007 at 5:42 am | Permalink

    q-2

    40 pins

Post a Comment

Your email is never published nor shared. Required fields are marked *

*
*