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Detailed Review of the 8085 Instruction Set

Detailed Review of the 8085 Instruction Set. 8085 Instruction Set. The 8085 instructions can be classified as follows: Data transfer operations Arithmetic operations (ADD, SUB, INR, DCR) Logic operations Branching operations (JMP, CALL, RET). Between registers

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Detailed Review of the 8085 Instruction Set

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  1. Detailed Review of the 8085 Instruction Set

  2. 8085 Instruction Set The 8085 instructions can be classified as follows: • Data transfer operations • Arithmetic operations (ADD, SUB, INR, DCR) • Logic operations • Branching operations (JMP, CALL, RET) • Between registers • Between memory location and a register • Direct write to a register / memory • Between I/O device and accumulator

  3. 8085 Instruction Types

  4. 8085 Instruction Types

  5. 8085 Instruction Types

  6. Simple Data Transfer Operations Examples: • MOV B,A 47 From ACC to REG • MOV C,D 4A Between two REGs • MVI D,47 16 Direct-write into REG D 47

  7. Simple Data Transfer Operations Example: • OUT 05 D3 05 Contents of ACC sent to output port number 05.

  8. Simple Memory Access Operations

  9. Simple Memory Access Operations

  10. Arithmetic Operations

  11. Arithmetic Operations

  12. Arithmetic Operations

  13. Arithmetic Operations

  14. Overview of Logic Operations

  15. Logic Operations

  16. Logic Operations

  17. Logic Operations

  18. Branching Operations Note: This is an unconditional jump operation. It will always force the program counter to a fixed memory address continuous loop !

  19. Branching Operations Conditional jump operations are very useful for decision making during the execution of the program.

  20. Example Write a 8085 machine code program: • Read two different memory locations • Add the contents • Send the result to output port 02 (display) if there is no overflow • Display “FF” if there is an overflow • Stop

  21. Example 2000 LDA 2050 3A 2001 50 2002 20 2003 MOV B,A 47 2004 LDA 2051 3A 2005 51 2006 20 2007 ADD B 80 2008 JNC XXYY D2 2009 YY 2010 XX 2011 MVI A,FF 3E 2012 FF 2013 OUT 02 D3 2014 02 2015 HLT 76 Load contents of memory location 2050 into accumulator Save the first number in B Load contents of memory location 2051 into accumulator Add accumulator with B Jump to YYXX if no carry ! Direct write FF into accumulator Display accumulator contents at output port 02 Stop

  22. Updated Code 2000 LDA 2050 3A 2001 50 2002 20 2003 MOV B,A 47 2004 LDA 2051 3A 2005 51 2006 20 2007 ADD B 80 2008 JNC 2013 D2 2009 13 2010 20 2011 MVI A,FF 3E 2012 FF 2013 OUT 02 D3 2014 02 2015 HLT 76 Load contents of memory location 2050 into accumulator Save the first number in B Load contents of memory location 2051 into accumulator Add accumulator with B Jump to 2013 if no carry ! Direct write FF into accumulator Display accumulator contents at output port 02 Stop

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