12-11-2012, 01:22 PM
OVERVIEW OF MICROCOMPUTER STRUCTURE AND OPERATION
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MICROPROCESSOR EVOLUTION AND TYPES
A common way of categorizing microprocessors is by the number of bits that their ALU can work with at a time. Microprocessor with a 4-bit ALU will be referred to asa 4-bit microprocessor, regardless of the number of address lines or the number of data lines that it has.
The first commercially available MP was the Intel 4004, produced in 1971. It contained 2300 PMOS transistors.
In 1972 Intel came out with the 8008, which was capable of working with 8-bit words. Along with this it required 20 more devices to work as CPU.
In 1974, Intel came out with the 8080 which had a much larger instruction set than 8008 and required only two additional devices to form functional CPU.
Soon after this Motorola came out with MC6800, another 8-bit general purpose CPU. It required only +5V. For many years they were the most sold MPs.
The other types of MPs are dedicated and embedded controllers, bit-slice processors and General purpose CPUs.The 8085 & 8086 come under the general purpose CPUs.
THE MICROPROCESSOR FAMILY –OVERVIEW
The Intel 8086 is a 16-bit MP that works as a CPU in a microcomputer. The term 16-bit means that it’s ALU, its internal registers, and most of its instructions are designed to work with 16-bit binary words. The 8086 has 16-bit data bus, so it can read data from or write data to memory and ports either16 bits or 8 bits at a time. The 8086 has a 20-bit address bus, so it can address any one of 220 , or 1,048,576, memory locations. Sixteen bit words will be stored in two consecutive memory locations. If the first byte if the word is at an even address, the 8086 can read the entire word in one operation. If the first byte of the word is at an odd address, the 8086 will read the first byte with one bus operation and the second byte with another bus operation.
The 8088 has the same ALU, the same registers, and the same instruction set as 8086. The 8088 has a 20 bit address bus, so it can address any one of 1,048,576 bytes in memory. The 8088 has 8 bit data bus so it can only read data from or write data to memory and ports, 8 bits at a time.
The Intel 80186 is an improved version of the 8086 and 80188 is the improved version of 8088. In addition to the 16 bit CPU 80186 and 80188 has programmable peripheral devices integrated in the same package.
The Intel 80286 is a 16 bit ,advanced version of the 8086 which is specifically designed for use as a CPU in a multiuser or multitasking microcomputer.80286 works as fast as 8086 and most programs written for 8086 can run for 80286.
With the 80386 processor, Intel started the 32 bit processor architecture, known as the IA-32 architecture. This architecture extended all the address and general purpose registers to 32 bits, which gave the processor the capability to handle 32 bit address, with 32 bit data. The Intel 80486 is the next member of the IA-32 architecture. This processor has the floating point processor integrated into CPU itself.
THE EXECUTION UNIT
The execution unit of the 8086 tells the BIU where to fetch instructions or data from, decades instructions, and executes instructions. It consists of control circuitry, instruction decoder and ALU. The control circuitry directs internal operations. A decoder in the EU translates instructions fetched from memory in to a se4ries of actions which the EU carries out. The EU has a 16-bit ALU which can add, subtract, AND, OR, XOR, increment, decrement, complement, or shift binary numbers.
Flag Register- A flag is a flip-flop that indicates some condition produced by the execution of an instruction or controls certain operation of EU. A 16-bit flag register contains nine active flags. Fig shows the location of nine flags in the flag register. Six of the nine flags are used to indicate some condition produced by an instruction.
The six conditional flags in this group are the carry flag(CF), the parity flag(PF), the auxillary flag(AF), the zero flag(ZF), the sign flag(SF), and the overflow flag(OF).
The three other flags in the flag register are used to control certain operations of the processor. The six conditional flags are set or reset by the EU on the basis of the results of some arithmetic and logic operation. The control flags are set or reset by the instructions in the program. The three control flags are trap flag(TF), which is used for single stepping through a program, the interrupt flag(IF), which is used to allow or prohibit the interruption of a program, and the direction flag(DF), which is used with string instructions.
INTRODUCTION TO PROGRAMMING THE 8086
Programming the 8086 can be done in two ways, Machine language and Assembly language programming. In Machine language programming a sequence of binary codes becomes the instructions to be executed. The binary form of the program is referred to as machine language it is the form required by the machine.
To make the programming easier many programmers write programs in assembly language. They then translate the assembly language program in to machine level language so that it can be loaded in to the memory and run. Assembly language statements are usually written in a standard form that has four fields.
[attachment=39081]
MICROPROCESSOR EVOLUTION AND TYPES
A common way of categorizing microprocessors is by the number of bits that their ALU can work with at a time. Microprocessor with a 4-bit ALU will be referred to asa 4-bit microprocessor, regardless of the number of address lines or the number of data lines that it has.
The first commercially available MP was the Intel 4004, produced in 1971. It contained 2300 PMOS transistors.
In 1972 Intel came out with the 8008, which was capable of working with 8-bit words. Along with this it required 20 more devices to work as CPU.
In 1974, Intel came out with the 8080 which had a much larger instruction set than 8008 and required only two additional devices to form functional CPU.
Soon after this Motorola came out with MC6800, another 8-bit general purpose CPU. It required only +5V. For many years they were the most sold MPs.
The other types of MPs are dedicated and embedded controllers, bit-slice processors and General purpose CPUs.The 8085 & 8086 come under the general purpose CPUs.
THE MICROPROCESSOR FAMILY –OVERVIEW
The Intel 8086 is a 16-bit MP that works as a CPU in a microcomputer. The term 16-bit means that it’s ALU, its internal registers, and most of its instructions are designed to work with 16-bit binary words. The 8086 has 16-bit data bus, so it can read data from or write data to memory and ports either16 bits or 8 bits at a time. The 8086 has a 20-bit address bus, so it can address any one of 220 , or 1,048,576, memory locations. Sixteen bit words will be stored in two consecutive memory locations. If the first byte if the word is at an even address, the 8086 can read the entire word in one operation. If the first byte of the word is at an odd address, the 8086 will read the first byte with one bus operation and the second byte with another bus operation.
The 8088 has the same ALU, the same registers, and the same instruction set as 8086. The 8088 has a 20 bit address bus, so it can address any one of 1,048,576 bytes in memory. The 8088 has 8 bit data bus so it can only read data from or write data to memory and ports, 8 bits at a time.
The Intel 80186 is an improved version of the 8086 and 80188 is the improved version of 8088. In addition to the 16 bit CPU 80186 and 80188 has programmable peripheral devices integrated in the same package.
The Intel 80286 is a 16 bit ,advanced version of the 8086 which is specifically designed for use as a CPU in a multiuser or multitasking microcomputer.80286 works as fast as 8086 and most programs written for 8086 can run for 80286.
With the 80386 processor, Intel started the 32 bit processor architecture, known as the IA-32 architecture. This architecture extended all the address and general purpose registers to 32 bits, which gave the processor the capability to handle 32 bit address, with 32 bit data. The Intel 80486 is the next member of the IA-32 architecture. This processor has the floating point processor integrated into CPU itself.
THE EXECUTION UNIT
The execution unit of the 8086 tells the BIU where to fetch instructions or data from, decades instructions, and executes instructions. It consists of control circuitry, instruction decoder and ALU. The control circuitry directs internal operations. A decoder in the EU translates instructions fetched from memory in to a se4ries of actions which the EU carries out. The EU has a 16-bit ALU which can add, subtract, AND, OR, XOR, increment, decrement, complement, or shift binary numbers.
Flag Register- A flag is a flip-flop that indicates some condition produced by the execution of an instruction or controls certain operation of EU. A 16-bit flag register contains nine active flags. Fig shows the location of nine flags in the flag register. Six of the nine flags are used to indicate some condition produced by an instruction.
The six conditional flags in this group are the carry flag(CF), the parity flag(PF), the auxillary flag(AF), the zero flag(ZF), the sign flag(SF), and the overflow flag(OF).
The three other flags in the flag register are used to control certain operations of the processor. The six conditional flags are set or reset by the EU on the basis of the results of some arithmetic and logic operation. The control flags are set or reset by the instructions in the program. The three control flags are trap flag(TF), which is used for single stepping through a program, the interrupt flag(IF), which is used to allow or prohibit the interruption of a program, and the direction flag(DF), which is used with string instructions.
INTRODUCTION TO PROGRAMMING THE 8086
Programming the 8086 can be done in two ways, Machine language and Assembly language programming. In Machine language programming a sequence of binary codes becomes the instructions to be executed. The binary form of the program is referred to as machine language it is the form required by the machine.
To make the programming easier many programmers write programs in assembly language. They then translate the assembly language program in to machine level language so that it can be loaded in to the memory and run. Assembly language statements are usually written in a standard form that has four fields.