Status register
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The document discusses status registers and shift registers used in digital circuits. A status register contains status bits that indicate the result of arithmetic logic unit (ALU) operations, including carry (C), sign (S), zero (Z), and overflow (V) bits. The carry bit is set if there is an output carry from the ALU, the sign bit is set if the highest order bit is 1, the zero bit is set if the ALU output is all zeros, and the overflow bit is set if the result is out of the ALU's range. Shift registers are used to shift data in digital circuits.
Status register
- 1. Status register and Shift register Design
- 2. Status registerRelative magnitude of two numbers may be determined by subtracting one from the other.Also called as flag bits or condition code bitsStatus BitsC – CarryS – Sign bitZ – zero bitV – Overflow bit
- 4. Status registerC – Carry bitSet if the output carry of ALU is 1S – Sign bitSet if the highest order bit is 1Z – Zero bitSet if the ALU’s output contains all zerosV - Overflow bitSet if there is any overflow. For a 8bit ALU, V is set if the result is greater than 127 and less than -128
- 5. (A-B) of unsigned numbers A and B are unsigned numbers
- 6. SHIFTER
- 7. Shifter