"I need keypad press to wake up microcontroller."

Are you locked into using that micro? http://www.goalsemi.com has an 8051 derivative with an "interrupt on port change" feature, although I did not look to see if that is also a wakeup source. There are other microcontroller families that do have an "interrupt/wake-up on port change" feature designed for just this type of thing. I'll avoid any explicit mention of the micro in this forum for fear that I might wake up in the middle of the night with someone trying to suffocate me with a pillow ;-) E-mail me if you want.