How will you create your NC files ? Some other PC program ?

What IS EIA code ? Does it contain X,Y in a two byte format ? The NC machine conversion I did had incremental X,Y pairs in a seven bit +sign format.

You shouldn't need to use an EPROM to store the data for your program- you would be better using a little serial memory.

There is no problem with the serial part, although I think you will need some handshaking protocol.

Steve