my interrupt procedure only loads the scancode of the pressed key into a buffer.
i'm comparing the value of the buffer outside the interrupt routine.

when i quickly press the up or down arrow nothing is wrong. even when i hold down the key. the counter increase or decrease.
the counter is 16-bits long.

when i quickly press up-down-up-down-etc... nothings is wrong. but when pressing both keys at the same time my program crash