I just did a little bit of looking around for dual port rams on Digikey and a few other distributors. I found an 8051-friendly part from Cypress (CY7C008-20AC): 64k x 8, 20ns, costs $35. At that price you would need a pretty good reason to use it. Of course you could choose a smaller part, say 2k of mem that costs $7. Depending on the project, that could be plenty.

You will still have to write code that handles contentions to make sure that valid data is being written and read. I am not sure what this involves. The only time I used a dual port ram was for a double buffer, so no two memory locations were ever simultaneously written to and read from.

- Lee