Bryan Parkoff wrote:
Please try to answer my one question. Do you think it is worth to use
GAL16V8 chip or ROM chip so Apple //e's RGBI port can be translated to Apple
IIgs' 16 colors using 12 bit look-up table in the GAL or ROM chip. Then D/A
chip or resistor network will give correct 16 colors (not 16 CGA colors).
Either approach will work just fine, Bryan, which one is 'better'
probably depends on what you've got in your electronics workshop.
I personally don't like the GAL approach, since that technology is
quite old and programmers don't seem to be easily available. It would
make it difficult for others to construct the circuit if they wanted
to.
Using ROMs is also workable, assuming you've got a ROM programmer
hanging around. It's probably simplest to use multiple ROMs, but you
could get away with one ROM and pair it up with an 8 bit latch.
My preferred approach is to use an 8-bit microcontroller, since these
are available everywhere, programmers are plentiful, and there's
software for every platform to program the things. You'd also end up
with a single-chip solution, which by my sense of hardware aesthetic is
the most 'elegant' design.
Others might consider that using 21st century to solve a 1980's
engineering problem is cheating - but you're building it, you get to
decide. Just pick an approach, run with it, and let us know how it
works out.