code: def REVSH(self, params):
          
          Ra, Rb = self.get_two_parameters(r'\s*([^\s,]*),\s*([^\s,]*)(,\s*[^\s,]*)*\s*', params)
  
          self.check_arguments(low_registers=(Ra, Rb))
  
          def REVSH_func():
              self.register[Ra] = ((self.register[Rb] & 0x0000FF00) >> 8) | \
                                  ((self.register[Rb] & 0x000000FF) << 8)
              if self.register[Ra] & (1 << 15):
                  self.register[Ra] |= 0xFFFF0000
  
          return REVSH_func
docs: REVSH
  
          Reverse the byte order in the lower half word in Rb and store the result in Ra.
          If the result of the result is signed, then sign extend