code: def ROR(self, a):
          
          r = (a >> 1) | (self.C << 7)
          self.clear_NZ()
          self.update_NZ_8(r)
          self.C = get_bit(a, bit=0) # same as: self.C = (a & 1)
          return r
docs: Rotates all bits of the register one place right through the C (carry)
          bit. This is a 9-bit rotation.
  
          moved the carry flag into bit 8
          moved bit 7 into carry flag
  
          source code forms: ROR Q; RORA; RORB
  
          CC bits "HNZVC": -aa-s