PicBasic Pro Compiler for 877A

Hello

I have some question about 16f877a.

1. How to make 16f877a to deal with two thing at a
same time?
(in other words ,receive data and put data into
EEPROM while it is dealing with the other thing.)
(or basic stamp2 can put data into 16f877a's
EEPROM while 877a is dealing with the other thing.)
2. I wote some code to drive RC servo
define osc 4
loop:
polsout 0,100
goto loop
sometimes servo works fine, but sometimes servo
moves very strange. but after 2 or 3 times reset, it become normal .
I can not find where is problem.


Thanks for anything you can offer.
Best Regards