1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

which bit specify the opcode , source , destination , and addressing mode ?

Discussion in '8051/8951' started by Parth86, Jan 19, 2015.

  1. Parth86

    Parth86 Member

    Joined:
    Dec 25, 2011
    Messages:
    515
    Likes:
    5
    hello ,

    I need help to understand how does instruction fetch , decode and execute

    Code (text):
    ORG 000
    MOV A,#55H ;load immediate value 55H into reg. A
    MOV R0,A  ; move the content of A into R0
    END
    CODE Memory
    Code (text):

    74 55 F8
    Code (text):
    ADDRESS                                          Value
    0000= 0000000000000000           74= 01110100
    0001= 0000000000000001           55= 01010101
    0002= 0000000000000010           F8= 11111000
    Processor read Byte from Program memory at the address indicate by program then it start to decode and execute the instruction

    MOV A,#55= 01110100 01010101 double byte instruction
    MOV R0, A = F8= 11111000 single byte instruction

    suppose we have 8 wires that tell the other part of processor to activate or deactivate
    suppose we have opcode 74= 01110100 ; that tell, Do mov Operation and activate Accumulator. here I don't understand how many wire tell that do mov operation , how many wire tell that activate Accumulator ?

    74=01110100

    I am reading 8051 instruction set I don't understand which bit specify the opcode , source , destination , and addressing mode ?
     
  2. Wade Hassler

    Wade Hassler Member

    Joined:
    Jun 4, 2009
    Messages:
    152
    Likes:
    11
  3. Parth86

    Parth86 Member

    Joined:
    Dec 25, 2011
    Messages:
    515
    Likes:
    5
    hello Wade Hassler,
    I have stopped working. I will come back But I don't know exact time, there are many people who always encourage me, always try to help me even I post stupid post. and Some people make me feel useless , stupid.
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. Ian Rogers

    Ian Rogers Super Moderator Most Helpful Member

    Joined:
    Mar 28, 2011
    Messages:
    9,170
    Likes:
    910
    Location:
    Rochdale UK

    vead
    Don't think like that... You can't ask stupid question... I really wish I could help you more, but to do that I would have to learn it myself.... I find your posts interesting and there are one or two that do answer... Your topic is very low level stuff, Its very hard to design a processor core ( rather you than me )...

    You have 89 views already, so there are many others waiting for the same answers... Some do not ask those questions and will be so glad that you do!!
     
    • Like Like x 1
  6. granddad

    granddad Active Member

    Joined:
    Jan 18, 2015
    Messages:
    750
    Likes:
    75
    Location:
    Worcestershire UK
  7. Parth86

    Parth86 Member

    Joined:
    Dec 25, 2011
    Messages:
    515
    Likes:
    5
    Hello Ian
    I like your way of communication and teaching methods. I seen in your every comment You always motivated me , You always tell me about positive thinking. also there are many members they always help me , they always try to give their best
     

Share This Page