code: def jtag_enable(self):
          
          status, _ = self.bulkCommand(_BMSG_ENABLE_JTAG)
          if status == 0:
              self._jtagon = True
          elif status == 3:
              self._jtagon = True
              raise JTAGAlreadyEnabledError()
          else:
              raise JTAGEnableFailedError("Error enabling JTAG. Error code: %s." %status)
docs: Enables JTAG output on the controller. JTAG operations executed
          before this function is called will return useless data or fail.
  
          Usage:
              >>> from proteusisc import getAttachedControllers, bitarray
              >>> c = getAttachedControllers()[0]
              >>> c.jtag_enable()
              >>> c.write_tms_bits(bitarray("001011111"), return_tdo=True)
              >>> c.jtag_disable()