Digital Electronics: Principles, Devices and Applications

532 Digital ElectronicsDemultiplexerGeneral PurposeRegistersMultiplexerMultiplexerArithmetic Logic Unit (ALU)FunctionSelectStatusStatusRegisterResultStackPointerData BusProgramCounterAddress BusControlUnitControl BusFigure 13.4Descriptive block diagram of a microprocessor.13.4.2 Arithmetic InstructionsArithmetic instructions performed by microprocessors include addition, subtraction, multiplication,division, comparison, negation, increment and decrement. It may be mentioned here that most of theeight-bit microprocessors do not support multiplication and division operations. These operations aresupported by the 16-bit and 32-bit microprocessors. The arithmetic operations supported by the 8085microprocessor are addition, subtraction, increment and decrement operations. Examples are as follows:ADD RADI eight-bitAdds the contents of the register to the accumulatorAdds the eight-bit data to the accumulator