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8085 microprocessor


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a quick and easy note on microprocessor.

a quick and easy note on microprocessor.

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  • 1. 8085 Microprocessor
  • 2. Architectural Differences betweenSAP1 And SAP2• 16 bit program Counter(16-bit address bus )• Loadable Program Counter(JMP instruction)• 2-input port , 2-output port• 64k Memory• Memory Data Register(MDR)• Temp, B, and C registers• Arithmetic and Logical Operations• Flags (Zero Flag and Sign Flag)• 8-bit Opcode,42 Instruction• Bidirectional Registers
  • 3. InstructionsMemory Reference Instruction :LDA , STA, MVIRegister Instruction:MOV, ADD, SUB, INR, DCRLogical Instruction:ORA/ORI, ANA/ANI, XRA/XRI,CMAJump and Return :JMP/JZ/JNZ/JM and CALL/RETOthers: IN, OUT, HLT, NOP, RAR, RAR
  • 4. Other Topics• Flags• T-State• Conditional Jumps
  • 5. Instruction affecting flagArithmetic and logical instructions:(ADD,SUB,INR,DCR, ANA/ANI,ORA/ORI, XRA/XRI)
  • 6. What you should know!!!• Architecture• Instructions• Basic Programming(Refer your books for several programmingexamples )
  • 7. Bonus QuestionWALP to divide 41H by 10H.(Hint: Repetitive subtraction. You may need useSign flag.)
  • 8. 80858085Architecture
  • 9. ALUBoth Arithmetic and Logical Operation:Operation PerformedAddition, Subtraction, Increment, Decrement, Logical AND, Logical OR, Logical XOR, Compare,Complement, Left/ Right Shift
  • 10. FlagsFive Flags Available in 8085Zero Flag(Z), Carry Flag(C), Auxiliary Carry(A),Sign Flag(S), Parity Flag (P)
  • 11. Timing and Control Signals• The timing and control unit synchronizes allthe microprocessor operations with the clockand generates the control signals necessaryfor communication between themicroprocessor and peripherals.
  • 12. INSTRUCTION REGISTER & DECODER:• When an instruction is fetched from memoryit is placed in instruction register. Then it isdecoded and encoded into various machinecycles.
  • 13. REGISTER ARRAY:• Apart from Accumulator (A-register), there aresix general-purpose programmable registers• B, C, D, E, H and L.• They can be used as 8-bit registers or paired tostore l6-bit data. The allowed pairs are B-C,D-Eand H-L.• The temporary registers W and Z are intendedfor internal use of the processor and it cannot beused by the programmer.
  • 14. Register Array:STACK POINTER (SP):• The stack pointer SP, holds the address of thetop of the stack.• The stack is used to save the content ofregisters during the execution of a program.
  • 15. Register Array:PROGRAM COUNTER (PC):The program counter (PC) keeps track of programexecution. To execute a program the startingaddress of the program is loaded in programcounter. The PC sends out an address to fetch abyte of instruction from memory and increment itscontent automatically. Hence, when a byte ofinstruction is fetched, the PC holds the address ofthe next byte of the instruction or next instruction.
  • 16. Address Bus• Consists of 16 address lines: A0 – A15• Operates in unidirectional mode: The addressbits are always sent from the MPU toperipheral devices, not reverse.• 16 address lines are capable of addressing atotal of 216 = 65,536 (64k) memory locations.• Address locations: 0000 (hex) – FFFF (hex)
  • 17. Data Bus• Consists of 8 data lines: D0 – D7• Operates in bidirectional mode: The data bitsare sent from the MPU to peripheral devices,as well as from the peripheral devices to themicroprocessor.• Data range: 00 (hex) – FF (hex)