I'll be glad to take a look at it if you supply me some more information. I'm a digital engineer and an assembly language guru but I need some basic information like:

1). what is a DDM4? Can you give me a URL to its pdf file?

2). can you give me a URL to the Atmel 89C2051 pdf file?

3). do you have an existing circuit board with other design constraints?
It can be hard to give circuit interface advice without knowing a lot about the microprocessors total requirements.

4). Do you have an existing microprocessor board you plan to use or will you be designing your own?

If no one arrives to give you a quick answer, I'll be glad to do some digging with the information you add.

Its strange but helping out with these other designs helps me clear my mind for what I'm working on.

-Jay C. Box