westfw:
Can you set up DMA to/from a set of IO pins, in a sort of traditional strobed "I've put data on these pins, and here's a signal to indicate that it's valid, so transfer that to/from memory" scheme? From brief reading of the datasheet, it looks like DMA to "ports" should be possible, but it was far less obvious whether you could get the sort of handshaking ancient devices expect...
The external RAM interface may be able to be persuaded to do this, but to me it seems like too much work and too may pins wasted to implement a "high speed" protocol on a 16 mhz chip......
Don't know about doing DMA to ports though... considering the horrible Harvard architecture it uses. The external memory interface connects to the "ram" side of the Harvard wall. The ports are on the other side, accessible only with special registers - don't see how DMA could "get through" that.