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A segment register is a register that contains the base address, or something related to the base address, of a region of memory. In the 8086/8088, the four segment registers are multiplied by 16 and added to the effective address to form the physical address.
An index register, on the other hand, is a register that contains an address that is added to another address to form the effective address.
In the 8086/8088, four address components are involved; 1.) the displacement contained within the instruction, often called the offset, 2.) a base address specified by the r/m field, often the BP or BX register, 3.) an index address specified by the r/m field, often the SI or DI register, and 4.) the segment address specified by context or by a segment override prefix, often the CS, DS, SS, or ES register.
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How many register are located in 8088microprocessor?
there are 14 registers in 8088 micro processor. All the 14 are 16 bit registers. They are4 segment registers viz - code segment register, stack segment register, data segment register, extra segment register.general registers are - accumulator register i.e. AX, base register i.e. BX, count register i.e. CX, data register i.e. DX and stack pointer (SP), base pointer (BP).index registers are - source index(SI), destination index(DI),and the other registers are instruction pointer and flags register.
What are the function of dI and sI register?
The SI (Source Index) and DI (Destination Index) registers are useful in repeated string operations, such as copy. The DS (Data Segment) register is paired up with SI and the ES (Extra Segment) register is paired up with DI.
What is the purpose of DI register in microprocessor in 8086?
DI is the Index register in Data segment(16-bit, 64 KB) .Destination Index (DI) is a 16-bit register. DI is used for indexed, based indexed and register indirect addressing, as well as a destination data address in string manipulation instructions.
A Explain the use of Code Segment CS and data segment DS register in 8086 microprocessor?
Code segment (CS) is a 16-bit register containing address of 64 KB segment with processor instructions. The processor uses CS segment for all accesses to instructions referenced by instruction pointer (IP) register. CS register cannot be changed directly. The CS register is automatically updated during far jump, far call and far return instructions. Data segment (DS) is a 16-bit register containing address of 64KB segment with program data. By default, the processor assumes that all data referenced by general registers (AX, BX, CX, DX) and index register (SI, DI) is located in the data segment. DS register can be changed directly using POP and LDS instructions. Code segment (CS) is a 16-bit register containing address of 64 KB segment with processor instructions. The processor uses CS segment for all accesses to instructions referenced by instruction pointer (IP) register. CS register cannot be changed directly. The CS register is automatically updated during far jump, far call and far return instructions. Data segment (DS) is a 16-bit register containing address of 64KB segment with program data. By default, the processor assumes that all data referenced by general registers (AX, BX, CX, DX) and index register (SI, DI) is located in the data segment. DS register can be changed directly using POP and LDS instructions.
What is default segment register for IP?
The default segment register for the Instruction Pointer (IP) in x86 architecture is the Code Segment (CS) register. This register is used to define the segment of memory that contains the currently executing code. When a program is executed, the CPU uses the CS register in conjunction with the IP register to determine the address of the next instruction to execute.
What are the different types of segment register?
The code segment (CS) register is used for access to program code. The data segment (DS) register is used for access to data. The extra segment (ES) register is used for access to data during certain string primitive operations. The stack segment (SS) register is used for access to stack data.Any of these implied uses can be overridden with a segment override prefix opcode.
What is the use of the extra segment in a 8086 processor?
extra segment is a 16-bit register containing address of 64KB segment, usually with program data. By default, the processor assumes that the DI register points to the ES segment in string manipulation instructions. ES register can be changed directly using POP and LES instructions. It is possible to change default segments used by general and index registers by prefixing instructions with a CS, SS, DS or ES prefix. any corrections most welcome
Give the segment registers and their corresponding offset registers?
Give the effective address if the segment register is AA03 and the offset register is 0200.
Draw the register organisation of 8086 and explain typical application of each register?
In the 8086/8088 microprocessor, there are eight 8 bit general registers, AH, AL, BH, BL, CH, CL, and DH, DL. They can be used as four 16 bit registers AX, BX, CX, and DX. There are four 16 bit pointer/index registers, SP (stack pointer), BP (base pointer), SI (source index), and DI (destination index). There are four 16 bit segment registers, CS (code segment), DS (data segment), SS (stack segment), and ES (extra segment). There is the 16 bit instruction pointer, IP, and there is a 16 bit flags register.
How the Memory Management Unit converts the logical addresses to physical addresses?
In the 8086/8088, the logical address corresponds to a segment register, such as CS (Code Segment), DS (Data Segment), SS (Stack Segment) and ES (Extra Segment). The segment register is selected by context, or it is explicitly selected using a segment override prefix. The segment register is left shifted 4 bits into a 20-bit temporary register. This is the same as multiplying it by 16. Then the logical address is added to that result. The final result is the physical address.
What is offset in segment register?
In computer architecture, an offset in a segment register refers to the specific address within a segment of memory that the segment register points to. Segment registers are used to divide memory into different segments, enabling easier access and management of data. The offset is added to the base address contained in the segment register to form the effective address of a memory location. This method allows for more efficient memory utilization and organization, particularly in systems with limited addressing space.
Which register can be changed directly using pop instruction in 8086?
stack segment register
