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How to lessen power consumption by setting address bus & data bus to "H"

Latest Updated:09/21/2010

Question:

I am using the MCU in the memory expansion mode. I want to decrease power consumption when in the stop mode by setting the address bus and data bus to "H". Is there any good way to do this?

Answer:

The bus retains the state at the time of the last access even after entering wait mode or stop mode. Therefore, it is not easy to enter wait mode or stop mode with pin state fixed to an arbitrary level in memory expansion mode or microprocessor mode.
However, if the processor mode is changed to single-chip mode, the pin used as the bus becomes a programmable I/O port, and can then be set to an arbitrary level by software.

  1. ‹Procedure›
  2. Change the processor mode to single-chip mode.
  3. Fix the programmable I/O port corresponding to the pin used as the bus to an arbitrary level by software.
  4. Enter wait mode or stop mode.

Notes:

  1. In memory expansion mode, allocate the above processing to the internal ROM area.
    In microprocessor mode, transfer the above processing to the internal RAM area and execute in the internal RAM.
  2. The control of the programmable I/O port mentioned in step 2 above must be performed after entering single-chip mode.

Other ways to suppress consumption current are described in the application note "Concept of the Power Control" (MEJ05B0130).
Please refer to the corresponding application note by going to the Document Library (http://www.renesas.com/document) and searching by Document Title or Document Number using Advanced Search.

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