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How should the P40/(VPP) pin be handled in QzROM version?

Latest Updated:12/01/2005

Question:

(Pin)  How should the P40/(VPP) pin be handled in QzROM version? [2005/12/01]

Answer:

When using the P40/(VPP) pin as an input port, connect a resistor of approximately 5kΩ in series as close as possible to the P40/(VPP) pin.
When the P40/(VPP) pin is not in use, connect the pin in the shortest and closest GND pattern to the GND supplying the VSS pin of the MCU. In addition, connecting a resistor of approximately 5kΩ in series to the GND may improve noise tolerance. In this situation, connect the pin in the shortest and closest GND pattern to the GND supplying the VSS pin of the MCU, as above.
(Explanation)
The P40/(VPP) pin of the QzROM version is the power source input pin for the built-in QzROM. When programming in the QzROM, the impedance of the P40/(VPP) pin is kept low to allow the writing current to flow into the built-in QzROM. Because of this, noise can enter easily. If noise enters the P40/(VPP) pin, instruction codes or data are not read correctly from the QzRoM, which may cause malfunction. (#105534)
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