Questions and Answers
The OUT instruction copies the contents of the ______ to the output port address.
accumulator
The LHLD instruction loads the contents of specified memory location to ______ register and contents of next higher location to H-register.
L
The SHLD instruction stores the contents of ______ register to specified memory location and contents of H register to next higher memory location.
L
The XCHG instruction exchanges ______ pair with HL pair.
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The ADD instruction is a ______ byte add instruction.
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The OUT instruction is a ______ byte instruction.
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The LHLD instruction is a ______ byte instruction.
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The microprocessor performs various arithmetic operations such as ______, subtraction, increment and decrement.
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The LXI instruction is used to load the ______ register with a 16-bit value.
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The SHLD instruction is the opposite of ______ instruction.
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Study Notes
Instruction Description and Format
- An instruction consists of two parts: operation code (Op-Code) field and operand or address field.
- Operand can be specified in various ways, including 8-bit or 16-bit data, internal register, memory location, or 8-bit or 16-bit address.
Instruction Format
- One address format (1 byte instruction): 1 byte is Op-code and operand is default.
Elements of Instruction Set
- Each instruction contains information required for execution by the processor.
- Elements of a machine instruction:
- Operation code (Op-code): specifies the operation to be performed (e.g. ADD, I/O).
- Source operand reference: inputs for the operation.
- Result operand reference: the result of the operation.
Examples of Instructions
- ADD R1, R0: adds the contents of R0 with the contents of R1 and stores the result in R1.
- OUT 8-bit address: copies the contents of the accumulator to the output port address specified in the 2nd byte.
- LHLD 16-bit address: loads the contents of the specified memory location to the L-register and the contents of the next higher location to the H-register.
- SHLD 16-bit address: stores the contents of the L-register to the specified memory location and the contents of the H-register to the next higher memory location.
- XCHG: exchanges the DE pair with the HL pair.
Arithmetic Group Instructions
- The 8085 microprocessor performs arithmetic operations such as addition, subtraction, increment, and decrement.
- Arithmetic operations have the following mnemonics:
- ADD R/M: 1 byte add instruction.
