Performs a logical shift right on the register. Shifts a zero into bit
        seven and bit zero into the C (carry) bit.

        source code forms: LSR Q; LSRA; LSRB

        CC bits "HNZVC": -0a-s

def LSR(self, a):
        """
        Performs a logical shift right on the register. Shifts a zero into bit
        seven and bit zero into the C (carry) bit.

        source code forms: LSR Q; LSRA; LSRB

        CC bits "HNZVC": -0a-s
        """
        r = a >> 1
        self.clear_NZC()
        self.C = get_bit(a, bit=0) # same as: self.C |= (a & 1)
        self.set_Z8(r)
        return r