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Questions and Answers
What is the role of interrupts in a computer system?
Which mode of operation is typically used for handling external interrupts in the 8086 processor?
In the 8086 microprocessor, what are some conditions that can cause interrupts?
Which aspect of a microprocessor's architecture allows it to address more than a megabyte of memory?
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What is the significance of the multiple addressing modes offered by the 8086 microprocessor?
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When an interrupt occurs in a computer system, what happens to the currently running program?
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Which segment descriptor does the extra segment in 8086 contain?
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In the 8086 architecture, which register holds the address of the next instruction to execute?
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Which flag in 8086 microprocessor is used to store information on whether an arithmetic operation has caused an overflow?
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Which type of instructions include ADD, SUB, ADC, SBB, and TEST in the 8086 microprocessor?
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What was one of the features provided by the 8288 chipset for the 8086 microprocessor?
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Which part does the stack segment point to in the 8086 memory map?
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Study Notes
Microprocessor 8086
The Intel 8086 is a versatile microprocessor made by Intel Corporation in 1978. It represents one of the first types of processors capable of addressing more than a megabyte of memory. This section covers various aspects of the 8086 microprocessor, including interrupts and interfacing, memory interfacing, the CPU's architecture, and pin diagrams.
Interrupts and Interfacing
Interrupts play a crucial role in the functioning of modern computers by allowing software to respond quickly to events occurring within hardware devices. In the case of the 8086 processor, interrupts can occur due to the following conditions:
- Real mode instruction fetch error.
- Overflow condition during data transfer.
- Stack segment limit exceeded.
- Breakpoint triggered.
- Trap or exception caused by instruction execution.
When an interrupt occurs, it takes control from the currently running program until the interrupt has been serviced. There are three modes of operation for servicing interrupts:
- Auto-vectored interrupt handler routine.
- Software interrupt handler routine.
- External interrupt handler routine.
Auto-vectored interrupt handlers are usually used when servicing hardware interrupts, while external interrupts are typically handled using software interrupt handlers.
Memory Interfacing
The 8086 microprocessor offers multiple addressing modes, which enable efficient access to different sections of memory. These modes include implicit direct addressing, indexing, base addressing, and relative addressing. The memory map of the 8086 consists of several segments: stack segment, extra segment, code segment, extra parity flag segment, and data segment.
The extra segment points to the top of each high memory block and contains the upper part of each segment descriptor. On the other hand, the stack segment points to the top of the current stack, which is typically located near the bottom of the highest available segment. By default, all segments have a size of 64 KB.
Architecture
The 8086 is a CISC (Complex Instruction Set Computer) processor with relative backward compatibility with earlier versions such as the 8080, 8085, and even the original 8008. The basic building blocks of the 8086 architecture include registers, flags, instructions, and chipsets. Some of these components are discussed below.
Registers
There are six general purpose registers on the 8086, also known as GPRs (General Purpose Registers): AX, BX, CX, DX, SP, and IP. Each register can hold either an unsigned or signed integer value, depending on its usage. For example, the IP (Instruction Pointer) holds the address of the next instruction to execute, while the SP (Stack Pointer) keeps track of the top of the stack.
Flags
Flags are typically set or cleared based on certain events during instructions. They serve as a means to store conditional information for branch operations. The most commonly used flags include CF (Carry Flag), ZF (Zero Flag), SF (Sign Flag), OF (Overflow Flag), PF (Parity Flag), AF (Auxiliary Carry Flag), TF (Trapping Flag), IF (Interrupt Flag), and DF (Direction Flag).
Instructions
The 8086 microprocessor is designed to execute various types of instructions. These include arithmetic operations, logical operations, input/output (I/O) instructions, and transfer instructions. Examples of arithmetic operations include ADD, SUB, ADC, SBB, and TEST. Logical operations include AND, OR, XOR, and NOT. Input/output instructions include IN, OUT, INS, and OUTS. Transfer instructions include MOV, LDS, LES, LEA, and MUL.
Chipsets
To expand the capabilities of the 8086 microprocessor, Intel developed various chipsets. One of the early add-on chipsets was the 8255, which offered a range of I/O peripherals. Another popular chipset was the 8288, which expanded the 8086's I/O capabilities and provided several features, such as DMA (Direct Memory Access) channels for faster data transfer.
Pin Diagrams
The 8086 microprocessor's pin diagram consists of several components, including the address bus, data bus, control bus, I/O bus, and power pins. The address bus is responsible for addressing memory locations, while the data bus facilitates data transfer between the microprocessor and other components. The control bus manages various operations within the microprocessor, such as interrupts and memory access. The I/O bus allows the microprocessor to communicate with external devices. Finally, the power pins provide the necessary power to operate the microprocessor.
In conclusion, the 8086 microprocessor is a versatile device that has paved the way for modern computing. Its features, such as interrupts and interfacing, memory interfacing, architecture, and pin diagrams, have contributed significantly to its success and the evolution of computer technology.
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Description
Explore the key aspects of the Intel 8086 microprocessor, including interrupts and interfacing, memory interfacing, CPU architecture, and pin diagrams. Test your knowledge on interrupt handling, memory addressing modes, register usage, flag manipulation, instruction set, and chipset expansion for the 8086 processor.
