Wednesday 31 August 2016
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INSTRUCTION WORD SIZE
- 8085 is an 8-bit microprocessor.
- It can handle 8-bits at a time.
- The memory location of 8085 microprocessor can accommodate 8-bits of data.
- To store 16-bits data, they are stored in two consecutive memory locations.
- The word length of an instruction can be :
- 1 byte / 1 word
- 2 bytes / 2 words
- 3 bytes / 3 words
1 - Byte Instructions
- They include opcode and operands in the same byte.
- Operands are internal registers and coded into the instruction.
- Instructions require one memory location to store single byte in the memory.
2 - Byte Instructions
- 1st byte specifies opcode and 2nd byte specifies operand.
- Instructions require two memory locations to store in the memory.
3 - Byte Instructions
- 1st byte specifies opcode and 2nd & 3rd bytes specifies 16-bit address
- 2nd byte holds the low order address.
- 3rd byte hods the high order address.
- Instructions require three memory locations to store single byte in the memory.
INSTRUCTION WORD SIZE
- 8085 is an 8-bit microprocessor.
- It can handle 8-bits at a time.
- The memory location of 8085 microprocessor can accommodate 8-bits of data.
- To store 16-bits data, they are stored in two consecutive memory locations.
- The word length of an instruction can be :
- 1 byte / 1 word
- 2 bytes / 2 words
- 3 bytes / 3 words
1 - Byte Instructions
- They include opcode and operands in the same byte.
- Operands are internal registers and coded into the instruction.
- Instructions require one memory location to store single byte in the memory.
2 - Byte Instructions
- 1st byte specifies opcode and 2nd byte specifies operand.
- Instructions require two memory locations to store in the memory.
3 - Byte Instructions
- 1st byte specifies opcode and 2nd & 3rd bytes specifies 16-bit address
- 2nd byte holds the low order address.
- 3rd byte hods the high order address.
- Instructions require three memory locations to store single byte in the memory.
INSTRUCTION FORMAT
- Each instruction has two parts :
- Opcode
- Operand
- Opcode is the code for the operation to be performed.
- It is also known as Machine Code.
- Operand is the data to be operated.
- Operand can be specified as :
- 8-bit data
- internal registers
- memory location
- 8-bit / 16-bit address
INSTRUCTION
- An instruction is a binary pattern designed inside the microprocessor to perform a specific function.
- In other words, it is actually a command to the microprocessor to perform a given task on specified data.
- An instruction set of microprocessor is a collection of instructions designed to perform specified operations on given data.
- It determines what functions the microprocessor can perform.
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