is a warm uC normal?

After testing my microcontroller in my circuit, everything seems to be OK so far, BUT as soon as I applied 12V to the VPP pin of my AT89C2051 uC, the temperature slowly rises in the microcontroller, but it never reaches the burning point. When I removed the 12V from the VPP and connected it to ground, the uC cools down and returns to normal temperature.

Is this normal operation?

um, no that is not normal. are you using a current-limiting resistor between 12v and the Vpp pin?

this sounds like the sort of thing that happens when the input pin protection diodes are trying to clamp the input to the supply rail... are you sure you're supposed to be applying 12 volts to that pin? I'm familiar with PICs, but not at all with atmels.