To answer Erik Malund's question:

This is a lab board I am designing for an undergraduate electronics class. It has a single channel A/D, single channel D/A, and 128k SRAM.

The board is supposed to demonstrate simple A/D concepts such as quantization and the Nyquist rate. It will also have "black box" modes where the students must figure out what kind of filter it is implementing.

Being able to swap out the P89C51RB2 (20MHz, 6clocks/cycle) to the DS89C420 (33MHz, 1clock/cycle) will enable filters with more coefficients. Plus I hope I can implement a simple FFT for fun.

Hope that helps.

- Lee Cross