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Note for Microprocessor - MP By Srikrishna Thota

  • Microprocessor - MP
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Srikrishna Thota
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Architecture of 8085     • Introduced in 1977. • It is 8-bit MP. • It is a 40 pin dual-in-line chip. • It uses a single +5V supply for its operations. • Its clock speed is about 3MHz.    History: When Intel made the first 4 bit microprocessor, it was called the 4004. At the time, they did not realize it was a microprocessor, they were just making a custom integrated circuit for a handheld electronic calculator. The instruction set on the 4004 was quite limited; an upgraded version was numbered 4040 by reversing the last two digits. When they made 8 bit processors, the double wide 4004 was the 8008, and the double wide 4040 was the 8080. The 8085 was the 5 volt only version of the 8080. The "5" in the model number came from the fact that the 8085 requires only a +5-volt (V) power supply rather than the +5V, −5V and +12V supplies the 8080 needed Three Units of 8085 1. Processing Unit 2. Instruction Unit 3. Storage and Interface Unit

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1. Processing Unit: • • • • Arithmetic and Logic Unit Accumulator Status Flags Temporary Register  2. Instruction Unit: • • • Instruction Register Instruction Decoder Timing and Control Unit  3. Storage and Interface Unit • • • • • • General Purpose Registers Stack Pointer Program Counter Increment/Decrement Register Address Latch Address/Data Latch Three Other Units • • • Interrupt Controller Serial I/O Controller Power Supply

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1. Processing Unit: Accumulator • • • • • • It the main register of microprocessor. It is also called register ‘A’. It is an 8-bit register. It is used in the arithmetic and logic operations. It always contains one of the operands on which arithmetic/logic has to be performed. After the arithmetic/logic operation, the contents of accumulator are replaced by the result. Arithmetic & Logic Unit (ALU) • • It performs various arithmetic and logic operations. The data is available in accumulator and temporary/general purpose registers. • Arithmetic Operations: Addition, Subtraction, Increment, Decrement etc. • Logic Operations: AND, OR, X-OR, Complement etc. Temporary Register • • • It is an 8-bit register. It is used to store temporary 8-bit operand from general purpose register. It is also used to store intermediate results

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