Hi Qiqiao,

Check out this thread http://www.8052.com/forum/read.phtml?id=2763

In fact if you serach the forum with terms like "Pulse generation" "square waves" you will get many hits and stuff to read through

It will give you some idea as to how go about doing things. But please note in the discussion you will not get much pointers to control the amplitude of the generated waves. What kind of control do you want in the amplitude ?

There is good PDF in the LINKS which gives much data, application details, sample code about the PCA that comes with 89c51rx2 chips and the like. Read that - quite interesting. Get it here http://www.intel.com/design/MC...085101.PDF

Raghu