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In which addressing mode the effective address of the operand is generated by adding a constant value to the content of a register?
its register indirect with displacement.
What is meant by effective address in microprocessor?
Effective address is the final address generated by offsetting and indexing which is sent to the virtual translation logic. It is the address of the operand in the virtual address space of the process, but not necessarily the address of the operand in the physical address space of the computer. In the 8085, efffective/virtual address is the same as physical address, because there is no virtual addressing logic in the 8085. In the 8086/8088, effective/virtual address is the same as physical address, but only in real mode. For example, in the 8086/8088, if the EBX register contains 1000000H, then the instruction MOV EAX,[EBX+1234H] has an effective address of 10001234H.
What is the consists in the Instruction register?
The Instruction Register contains the current instruction being executed. It is an internal, special register, and you can not do anything explicit with it. If you are referring to the Program Counter, that simply contains the address of the next instruction to execute. It is incremented for each opcode and operand byte fetched.
What are the differences between preindexing and postindexing?
post indexing First, the contents of the address field are used to access a memory location containing a direct address. This address is then indexed by the register value. pre-indexing An address is calculated as with simple indexing. In this case, however, the calculated address contains not the operand, but the address of the operand.
What is the difference between register addressing mode and register indirect addressing mode?
Ans: In the register addressing mode the operands are in registers which reside within the CPU. Register-mode instructions are 1-byte instructions and can be executed within the CPU without the need to reference memory for operands. But in the Register-indirect addressing mode the instruction specifies a register or a pair of registers in the processor whose contains give the address of the operand in memory. This mode uses 1-byte instructions even though the operand is in memory. Before using a register-indirect mode instruction, the programmer must ensure that the address of the operand is placed in the processor register with a previous transfer-type instruction. A reference to the register is then equivalent to specifying a memory address.
What is the difference between a direct and indirect address instruction how many references to memory are needed for each type of instruction to bring an operand into a processor register?
Direct address instructions specify the memory location of the operand directly within the instruction itself, requiring only one memory reference to fetch the operand. In contrast, indirect address instructions specify a memory location that contains the address of the operand, necessitating two memory references: one to retrieve the address and another to fetch the operand itself. Therefore, direct addressing is more efficient in terms of memory access.
What are operands?
Every instruction contains to parts: operation code[opcode],and operand. The first part of an instruction which specifies the task to be performed by the computer is called opcode. The second part of the instruction is the data to be operated on.,and it is called operand. The operand[or data]given in the instruction may be in various forms such as 8-bit or 16-bit data, 8-bit or 16-bit address, internal register or a register or memory location.
Instruction cycle with indirect?
In an instruction cycle with indirect addressing, the CPU fetches the instruction, decodes it to determine the memory address of the operand stored in a register, fetches the operand from the memory location pointed to by the register, and executes the instruction using the operand. Finally, the CPU stores the result back in memory if needed. This extra step of fetching the operand based on the indirect memory address adds complexity to the instruction cycle.
Why accumulator is called a special register?
Accumulator contains one of the operand for any operation which is performed by the ALU.The result of the operation is stored in the Accumulator. thus it is a special register
List different address modes of 8051micro controller with example?
The 8051 microcontroller employs several addressing modes, including: Immediate Addressing Mode: The operand is specified in the instruction itself. Example: MOV A, #25H moves the hexadecimal value 25 into the accumulator. Register Addressing Mode: The operand is in a register. Example: MOV A, R0 moves the content of register R0 into the accumulator. Direct Addressing Mode: The operand's address is given directly in the instruction. Example: MOV A, 30H moves the content of memory location 30H into the accumulator. Indirect Addressing Mode: The address of the operand is held in a register. Example: MOV A, @R1 moves the content of the memory location pointed to by register R1 into the accumulator.
What is register indirect addressing mode in 8086?
In the 8086 microprocessor, register indirect addressing mode is a method of accessing data in memory using a register to hold the address of the data. In this mode, the effective address of the operand is provided by a register, such as BX, SI, or DI. This allows for flexible data manipulation, as the contents of the register can be easily modified to point to different memory locations. This addressing mode is particularly useful for operations on arrays and data structures.
What is the use of base pointer register?
It contains an address, which will be used in calculting the actual address of an operand. Example (Sytem/360): L R2,12(R3,R4) meaning: tempadd := 12 + R3 + R4 R2 := content of memory at tempadd here R3 is called base registed, R4 is called index register. Or vice versa.
