MCBX51: PRESSING INT1 CAUSES A RESET

Information in this article applies to:

• MCBx51 Evaluation Boards

SYMPTOM

When using an AT89C51ED2 or AT89C51RD2 pressing the button NMI/INT1 may cause an restart of the application. This even happens when J4 and/or J5 are not closed.

CAUSE

The capacitor C6 on the MCBx51, which is used to debounce the push button, is oversized. When pressing the button the supply voltage will drop off. On microcontrollers with a power monitor, this may trigger an chip-internal reset.

RESOLUTION

You may either remove C6 completely or you may replace it with one with a smaller capacity. 33nF would be suitable for the AT89C51ED2/RD2.

MORE INFORMATION

• Refer to Schematics in the MCBx51 User's Guide.

SEE ALSO

• Atmel AT89C51x2 Datasheet

Last Reviewed: Sunday, November 19, 2006