On Wed, Nov 25, 2009 at 01:33, Jim Brain <brain at jbrain.com> wrote:
?2. Anyone on list have any experience with MAX 7032A
Altera CPLDs? ? ? I'm
working on a VIC-20 MIDI interface for a friend in Toronto,
? ? and I'd love to use a small CPLD to make it more cost effective to
? ? produce the MIDI cart. ?I've found TQFP 7032A units for
? ? $.31/piece, but I've never done CPLD. ?I want to learn, and
? ? thought if I at least knew someone could help me though the first
? ? few bits (and help with the programming cable, etc., it'd be much
? ? easier.
I'm currently teaching myself VHDL using the free Xilinx tools ("ISE
Webpac" or something), using a Spartan3E board and parallel JTAG cable
that was given away at an academic trade show. I think the parallel
JTAG cable can be rebuilt very cheaply; it's just a few level
shifters. Xilinx has a schematic in the JTAG programmer guide.
Universities can be good sources of older FPGA/CPLD development tools
too; about 2 or 3 years ago, McGill (where I am) tossed out nice
Altera boards, and I'm still kicking myself for not grabbing one.
I'm planning to use the Xilinx chips with my old Commodore stuff too,
and one of the problems is the use of 3.3V rather than 5V logic. The
official recommendation from Xilinx for their Spartan devices is to
use simple resistor for connecting 5V out to 3.3V in, and just connect
straight-through for 3.3V out to 5V in. I have no idea how I'd handle
a bidirectional port though; is a resistor good enough or is a level
shifter needed?
Or I could try to find programmable 5V parts instead...
What have you been doing on your replacement ROM parts? (though I
guess on a rom all pins are strictly unidirectional :-)
--
Joachim Thiemann ::
http://www.tsp.ece.mcgill.ca/~jthiem