04-02-2013, 03:41 PM
INTEL MICROPROCESSORS 8086/8088
[attachment=49572]
SALIENT FEATURES:
8086 is the first 16-bit microprocessor from INTEL, released in the year 1978 . It is a 40 pin DIP chip based on N-channel, depletion load silicon gate technology(HMOS). The term 16 bit means that its ALU,its internal registers and most of the instructions are designed to work with 16 bit binary words.8086 is available at different clock speeds Viz, 5 M.Hz(8086);8M.Hz(8086-2) and 10(8086-1) M.Hz .8086 microprocessor has a 16-bit data bus and 20-bit address bus. So, it can address any one of 220 =1048576=1 mega byte memory locations. INTEL 8088 has the same ALU ,same registers and same instruction set as the 8086.But the only difference is 8088 has only 8-bit data bus and 20-bit address bus. Hence the 8088 can only read/write/ports of only 8-bit data at a time .The 8088 was used as the CPU in the original IBM personal computers [ IBMPC/XT] .The 8086 microprocessor can work in two modes of operations .They are Minimum mode and Maximum mode. In the minimum mode of operation the microprocessor do not associate with any co-processors and can not be used for multiprocessor systems. But in the maximum mode the 8086 can work in multi-processor or co-processor configuration. This minimum or maximum operations are decided by the pin MN/ MX(Active low). When this pin is high 8086 operates in minimum mode otherwise it operates in Maximium mode.
ARCHTECTURE OF 8086/8088 :
To improve the performance by implementing the parallel processing concept the CPU of the 8086 /8088 is divided into two independent sections .They are Bus Interface Unit (BIU) and Execution Unit.(EI).The BIU sendsout addresses ,fetches instructions ,read data from ports and memory and writes data to ports
and memory.i.e the BIU handles all transfers data and addresses on the buses required by the execution Unit . Whereas the Execution Unit decodes the instructions and executes the instructions
The Execution Unit : The Execution Unit consists of a control system , a 16-bit ALU, 16-bit Flag register and four general purpose registers(AX,BX,CX,DX), pointer registers (SP,BP) and Index registers(SI,DI) of each 16-bits .
The control circuitry controls the internal operations .The decoder in the execution unit decodes the instructions fetched from the memory into a series of actions. The ALU can add ,subtract, perform operations like logical AND,OR,XOR, increment, decrement, complement ,and shifting the binary numbers.
Bus Interface Unit : The BIU consists of a 6-byte long instruction register called Queue.
And four stack segment registers (ES,CS,SS,DS) , one Instruction Pointer(IP) and an adder circuit to calculate the 20bit physical address of a location. This bus interface unit will perform all the external bus operations. They are fetching the instructions from the memory, read/write data from/into memory or port and also supporting the instruction Queue etc. The BIU fetches up to six instruction bytes from the memory and stores these pre-fetched bytes in a first –in first out register set called Queue. When the execution unit is ready for the execution of the instruction ,instead of fetching the byte from the memory ,it reads the byte from the Queue .This will increase the overall speed of microprocessor .Fetching the next instruction while the current instruction executes is called pipelining or parallel processing.
8086 PIN DIAGRAM – PIN DESCRIPTION
Intel 8086 is a 16-bit HMOS microprocessor. It is available in 40 pin DIP chip. It uses a 5V d.c. supply for its operation. The 8086 uses 20-line address bus. It uses a 16-line data bus. The 20 lines of the address bus operate in multiplexed mode. The 16-low order address bus lines are multiplexed with data and 4 high-order address bus lines are multiplexed with status signals. The pin diagram of Intel 8086 is shown in Fig.4.
AD0-AD15 (Bidirectional) : Address/Data bus. These are low order address bus. They are multiplexed with data. When AD lines are used to transmit memory address the symbol A is used instead of AD, for example A0-A15. When data are transmitted over AD lines the symbol D is used in place of AD, for example D0-D7, D8-D15 or D0-D15.
MEMORY ORGANIZATION :
The 8086 processor provides a 20-bit address toaccess any location of the 1 MB memory space. The memory is organized as a linear array of 1 million bytes, addressed as 00000(H) to FFF(H). The memory is logically divided into code, data, extra data, and stack segments of up to 64K bytes each . Physically, the memory is organized as a high bank (D15 - D8) and a low bank (D7 –D0) of 512 K 8-bitbytes addressed in parallel by the processor's address lines A19 -A1. Byte data with even addresses is transferred on the D7 – D0 bus lines while odd addressed byte data (A0 HIGH) is transferred on the D15-D8 bus lines. The processor provides two enable signals, BHE and A0 , to selectively allow reading from or writing into either an odd byte location, even byte location, or both. The instruction stream is fetched from memory as words and is addressed internally by the processor to the byte level as necessary.
[attachment=49572]
SALIENT FEATURES:
8086 is the first 16-bit microprocessor from INTEL, released in the year 1978 . It is a 40 pin DIP chip based on N-channel, depletion load silicon gate technology(HMOS). The term 16 bit means that its ALU,its internal registers and most of the instructions are designed to work with 16 bit binary words.8086 is available at different clock speeds Viz, 5 M.Hz(8086);8M.Hz(8086-2) and 10(8086-1) M.Hz .8086 microprocessor has a 16-bit data bus and 20-bit address bus. So, it can address any one of 220 =1048576=1 mega byte memory locations. INTEL 8088 has the same ALU ,same registers and same instruction set as the 8086.But the only difference is 8088 has only 8-bit data bus and 20-bit address bus. Hence the 8088 can only read/write/ports of only 8-bit data at a time .The 8088 was used as the CPU in the original IBM personal computers [ IBMPC/XT] .The 8086 microprocessor can work in two modes of operations .They are Minimum mode and Maximum mode. In the minimum mode of operation the microprocessor do not associate with any co-processors and can not be used for multiprocessor systems. But in the maximum mode the 8086 can work in multi-processor or co-processor configuration. This minimum or maximum operations are decided by the pin MN/ MX(Active low). When this pin is high 8086 operates in minimum mode otherwise it operates in Maximium mode.
ARCHTECTURE OF 8086/8088 :
To improve the performance by implementing the parallel processing concept the CPU of the 8086 /8088 is divided into two independent sections .They are Bus Interface Unit (BIU) and Execution Unit.(EI).The BIU sendsout addresses ,fetches instructions ,read data from ports and memory and writes data to ports
and memory.i.e the BIU handles all transfers data and addresses on the buses required by the execution Unit . Whereas the Execution Unit decodes the instructions and executes the instructions
The Execution Unit : The Execution Unit consists of a control system , a 16-bit ALU, 16-bit Flag register and four general purpose registers(AX,BX,CX,DX), pointer registers (SP,BP) and Index registers(SI,DI) of each 16-bits .
The control circuitry controls the internal operations .The decoder in the execution unit decodes the instructions fetched from the memory into a series of actions. The ALU can add ,subtract, perform operations like logical AND,OR,XOR, increment, decrement, complement ,and shifting the binary numbers.
Bus Interface Unit : The BIU consists of a 6-byte long instruction register called Queue.
And four stack segment registers (ES,CS,SS,DS) , one Instruction Pointer(IP) and an adder circuit to calculate the 20bit physical address of a location. This bus interface unit will perform all the external bus operations. They are fetching the instructions from the memory, read/write data from/into memory or port and also supporting the instruction Queue etc. The BIU fetches up to six instruction bytes from the memory and stores these pre-fetched bytes in a first –in first out register set called Queue. When the execution unit is ready for the execution of the instruction ,instead of fetching the byte from the memory ,it reads the byte from the Queue .This will increase the overall speed of microprocessor .Fetching the next instruction while the current instruction executes is called pipelining or parallel processing.
8086 PIN DIAGRAM – PIN DESCRIPTION
Intel 8086 is a 16-bit HMOS microprocessor. It is available in 40 pin DIP chip. It uses a 5V d.c. supply for its operation. The 8086 uses 20-line address bus. It uses a 16-line data bus. The 20 lines of the address bus operate in multiplexed mode. The 16-low order address bus lines are multiplexed with data and 4 high-order address bus lines are multiplexed with status signals. The pin diagram of Intel 8086 is shown in Fig.4.
AD0-AD15 (Bidirectional) : Address/Data bus. These are low order address bus. They are multiplexed with data. When AD lines are used to transmit memory address the symbol A is used instead of AD, for example A0-A15. When data are transmitted over AD lines the symbol D is used in place of AD, for example D0-D7, D8-D15 or D0-D15.
MEMORY ORGANIZATION :
The 8086 processor provides a 20-bit address toaccess any location of the 1 MB memory space. The memory is organized as a linear array of 1 million bytes, addressed as 00000(H) to FFF(H). The memory is logically divided into code, data, extra data, and stack segments of up to 64K bytes each . Physically, the memory is organized as a high bank (D15 - D8) and a low bank (D7 –D0) of 512 K 8-bitbytes addressed in parallel by the processor's address lines A19 -A1. Byte data with even addresses is transferred on the D7 – D0 bus lines while odd addressed byte data (A0 HIGH) is transferred on the D15-D8 bus lines. The processor provides two enable signals, BHE and A0 , to selectively allow reading from or writing into either an odd byte location, even byte location, or both. The instruction stream is fetched from memory as words and is addressed internally by the processor to the byte level as necessary.