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Arithmetic And Logic Unit

Date: 10 Apr 2013

Arithmetic and Logic Unit (ALU) in microprocessor is capable of performing the following operations on binary data.

  1. Binary addition and subtraction
  2. Logical AND, OR, XOR
  3. Complement
  4. Rotate left and right

ALU has three registers: accumulator, temporary register and flag register (SR). Accumulator and temporary register are used to hold the operand of the operations being performed. The result of the operation is again placed in the accumulator replacing all the existing original operands.

The ALU contains number of flip-flops called flags to store information related to the result of the operation. The information may be sign of the result, carry status, result is 0 or not, parity etc. Decimal adjust is an additional unit used to adjust the result of the addition operation.

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    1. […] registers in microprocessor are utilized by ALU and the control section for temporary storage of instruction, operands or address at various stages […]