describe the role and effect of quantum tunneling on non-volatile memory devices (including types of flash memory)

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  Nonvolatile memory (NVM) is a special physical medium that can reserve the stored magnetic cells without electric power. NVM exists in almost all the industrial control systems to keep some important parameters and working data such as devices’ physical and mechanical attributes, system install, and configuration parameters and programmed timer values, and so on. Industrial control systems take advantage of the NVM to be quickly and precisely established at a Power-on as well as correctly execute software processes.

  To check and to modify the NVM attributes is one of the important measures for finding out the root reason when a software process crashes. The NVM Read and Write Routines are designed for helping the Process diagnostics.

  An industrial control system can have more than one NVM, each of them being connected through either PCI bus or internal bus with one microprocessor. Through the bus system, a microprocessor can communicate with the corresponding hardware controller of the respective NVM to accomplish the read or write operation.

  To issue the NVM Read and Write Routines, the application programs of the microprocessor-unit board linking with the NVM hardware controller establish a list of the NVM elements (called the NVM attributes list) to be tested. A unique ID to be discriminated from others should identify each of the NVM elements in this list.

  In general, the NVM Read and Write Routines, once starting, follow the procedure given below:

  (1)Change the system mode into a diagnostic mode,

  (2)Start either NVM Read Routines or NVM Write Routines,

  (3)Select one NVM element by its ID from the system’s NVM attributes list,

  (4)Send the command to the hardware controller of the NVM to start this read or write operation,

  (5)Communicate with the hardware controller of the NVM for the result of reading or writing and display the results if allowable,

  (6)Send the command to the hardware controller of the NVM to stop this read or write operation,

  (7)Select another NVM attribute and repeat the above steps to test…,

  (8)Stop either NVM Read Routines or NVM Write Routines,

  (9)Change the system mode from the current diagnostic mode back to a normal mode.

  Many non-volatile memories (including types of Flash memory) use floating gate transistors like this one. Like many transistors, it has three important terminals: the source, the drain and the control gate. In a normal (non-floating) transistor applying a voltage on the gate will create a channel between the source and the drain that allows current to flow between the source and drain. A floating gate transistor adds a layer of metal between two very thin layers of insulation (the oxide) so that the floating gate is electrically disconnected from everything around it. If we apply a high voltage on the control gate and across the gate-source terminals, electrons crossing the channel will start moving really fast. Fast as they are, they still don't have enough energy to travel in the oxide, but if the oxide layer is thin enough the uncertainty principle allows some of the fast electrons to "jump through" the oxide layer and land in the floating gate. Once in the oxide, the electrons are trapped (again, oxide won't let them flow in or out), and the gate becomes fixed in the "on" or "off" position ('1' or '0' for data storage). This jump across the oxide is quantum tunneling: without quantum mechanics, not enough electrons would be able to reach the floating gate and we couldn't set the transistor.

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