Architecture of 80286
Shows the block diagram of an INTEL microprocessor. The80286 is divided into four subunits.
1- Bus Unit 2- Address Unit
3-Execution 4- Instruction Unit
1- Bus Unit
It includes address latches and data transceivers, bus interface and control circuitry, instruction prefetches and a 6-byte instruction queue. The bus unit dies all the memory and I/O read/write Operations. When the BU is not using the buses for the other operations, It prefetches instruction bytes and puts them in a 6-byte prefetch queue.
In case of JUMP and CALL instructions queue must be dumped and reloaded from the destination address. The bus unit is responsible
2- Address Unit
This is a unidirectional bus, because information flows over it in only one direction, from the CPU to the memory or I/O elements. The CPU alone can place logic levels on the lines of the address bus, thereby generating 216 = 65,536 different possible addresses. Each of these addresses corresponds to one memory location or one I/O element. When the CPU wants to communicate (read or write) with a certain memory location or I/O device, it places the appropriate 16-bit address code on its 16 address pin outputs, A0 through A15, and onto the address bus.
An arithmetic and logic unit and, indeed, all electronic components in the computer are based on the use of simple digital logic devices that can store binary digits and perform simple Boolean logic operations.
3-Execution
The ALU is the area of the computer in which arithmetic and logic operations are performed on data. The type of operation that is to be performed is determined by signals from the control unit. The data that are to be operated on by the ALU can come from either the memory unit or the input unit. Results of operations performed in the ALU can be transferred to either the memory unit for storage or the output unit.
4- Instruction Unit
he controls unit fetches an instruction from memory by sending an address and read command. The instruction word stored at the memory location is then transferred to the control unit. This instruction word, which is in some form of binary code, is then decoded by logic circuitry in the control unit to determine which instruction is being called for. The control unit uses this information to send the proper signals to the rest of the units in order to execute the specified operation.
The devices that make up the input and output units are called peripherals because they are external to the rest of the computer. The most important aspect of peripherals involves interfacing. Computer interfacing is specifically defined as transmitting digital information between a computer and its peripherals in a compatible and synchronized way
Shows the block diagram of an INTEL microprocessor. The80286 is divided into four subunits.
1- Bus Unit 2- Address Unit
3-Execution 4- Instruction Unit
1- Bus Unit
It includes address latches and data transceivers, bus interface and control circuitry, instruction prefetches and a 6-byte instruction queue. The bus unit dies all the memory and I/O read/write Operations. When the BU is not using the buses for the other operations, It prefetches instruction bytes and puts them in a 6-byte prefetch queue.
In case of JUMP and CALL instructions queue must be dumped and reloaded from the destination address. The bus unit is responsible
2- Address Unit
This is a unidirectional bus, because information flows over it in only one direction, from the CPU to the memory or I/O elements. The CPU alone can place logic levels on the lines of the address bus, thereby generating 216 = 65,536 different possible addresses. Each of these addresses corresponds to one memory location or one I/O element. When the CPU wants to communicate (read or write) with a certain memory location or I/O device, it places the appropriate 16-bit address code on its 16 address pin outputs, A0 through A15, and onto the address bus.
An arithmetic and logic unit and, indeed, all electronic components in the computer are based on the use of simple digital logic devices that can store binary digits and perform simple Boolean logic operations.
3-Execution
The ALU is the area of the computer in which arithmetic and logic operations are performed on data. The type of operation that is to be performed is determined by signals from the control unit. The data that are to be operated on by the ALU can come from either the memory unit or the input unit. Results of operations performed in the ALU can be transferred to either the memory unit for storage or the output unit.
4- Instruction Unit
he controls unit fetches an instruction from memory by sending an address and read command. The instruction word stored at the memory location is then transferred to the control unit. This instruction word, which is in some form of binary code, is then decoded by logic circuitry in the control unit to determine which instruction is being called for. The control unit uses this information to send the proper signals to the rest of the units in order to execute the specified operation.
The devices that make up the input and output units are called peripherals because they are external to the rest of the computer. The most important aspect of peripherals involves interfacing. Computer interfacing is specifically defined as transmitting digital information between a computer and its peripherals in a compatible and synchronized way
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