At 70ns, I can make the design pretty simple by using an EEPROM. I did some trial synthesis targeting a Lattice MachXO2 part, and I think I could get the speed down into the 20ns range that way, at the cost of a more complex board design and needing to use Lattice's synthesis tool to prepare programming data.
-- Mark J. Blair, NF6X <n...@nf6x.net> http://www.nf6x.net/
