Query regarding Microcontroller 8051

Replies

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  Jeffrey Arulraj

  The Zero Flag in MC8051 is not present.
  
  JNC, JC and all check the status of the Carry flag to do all the operations you have asked here for
  
  Have fun exploring 8051
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  sparsh sharma

  Jeffrey Samuel

  The Zero Flag in MC8051 is not present.
  
  DJNZ and all check the status of the Carry flag to do all the operations you have asked here for
  
  Have fun exploring 8051

  Thank you Sir, but i have one doubt that DJNZ means jump if contents of register A is not zero, so where is carry flag effected in DJNZ instruction, will you please clarify your answer.........
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  Jeffrey Arulraj

  sparsh sharma

  Thank you Sir, but i have one doubt that DJNZ means jump if contents of register A is not zero, so where is carry flag effected in DJNZ instruction, will you please clarify your answer.........

  Sorry about that I made a small error I corrected it
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  sparsh sharma

  Jeffrey Samuel

  Sorry about that I made a small error I corrected it

  sir i just want to know that how microcontroller gets notification about the contents of accumulator
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  Harshad Italiya

  sparsh sharma

  sir i just want to know that how microcontroller gets notification about the contents of accumulator

  I didn't get this question. Accumulator is part of Microcontroller itself. No need for microcontroller to get notification from accumulator.
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  sparsh sharma

  Harshad Italiya

  I didn't get this question. Accumulator is part of Microcontroller itself. No need for microcontroller to get notification from accumulator.

  i mean as in case of microprocessor there is a zero flag which becomes high when accumulator contents become zero then why is it not present in the microcontroller
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  Harshad Italiya

  sparsh sharma

  i mean as in case of microprocessor there is a zero flag which becomes high when accumulator contents become zero then why is it not present in the microcontroller

  Microprocessor and Microcontroller are two different things. 8051 is Microcontroller and 8051 has Zero flag.
  
  Sorry but I am still not getting things clear about your questions.
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  sparsh sharma

  Harshad Italiya

  Microprocessor and Microcontroller are two different things. 8051 is Microcontroller and 8051 has Zero flag.
  
  Sorry but I am still not getting things clear about your questions.

  sir, my question is without any zero flag how microcontroller decides that now the contents of A-register has become zero ? like in case of carry instructions (jnc, jc etc) there is a carry flag to give indication about the carry. then why zero flag is not there.
• 

  Murthy Yayavaram

  Dear Friend, the Zero flag is an indication of status of CPU after some arithmetic operation.O.K. Normally in microprocessors, this status is used to implement some condition .While implementing the condition (for ex say branch condition) the CPU will check the status of this zero flag and act accordingly.But in the case of 8051 micro controller ,the accumulator can be made zero by other instructions also and the same status can be checked using J Z ,JNZ etc...So the controller can manage without zero flag also. hope I am clear ..