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vhdlfpgaalu

how does ALU work?


Implementing 8bit ALU in VHDL with unsigned numbers only. When the result of the sum is (1)00000000, 1 being the carry out, should the zero flag of the ALU be set to 1? Or the result is considered to be different from 0?


Solution

  • (answer from regular CPU point of view... - i.e. http://z80-heaven.wikidot.com/flags-and-bit-level-instructions )

    I'd expect if (result) to chose false branch after such operation. So it feels like zero flag should be set along with carry flag.