Re: 6502 VHDL core?

From: Scott McDonnell (
Date: 2006-03-01 13:03:20

----- Original Message ----- 
From: "Wouter Coene" <>
To: <>
Sent: Tuesday, February 28, 2006 2:06 PM
Subject: Re: 6502 VHDL core?

> According to fachat (
>> Does anyone have experience with this or VHDL/FPGAs in general?
>> Any hints on which system might be easy to use (e.g. programmable by
>> RS232)?
> FPGA's (which don't retain their configuration when turned off btw) are
> generally programmed using JTAG or an on-board programming chip. JTAG is a
> simple bit-serial protocol that can be driven from a PC's parallel port
> using some 74-series logic.

Some FPGAs do retain thier configuration when turned off. Lattice, Actel, 
Altera, and probably the rest of the FPGA players have this technology 
(granted it is a bit more
expensive.) These are called Flash FPGAs. Some FPGAs also have the ability 
to directly connect to configuration ROMs (special ROM that increments by 
itself) There are even FPGAs and CPLDs with RAM and ROM built in (usually 
called SoCs for System on Chip.) Then there are also FPAAs which
are FPGAs analog counterpart, good for SID filter creation or VIC video 
creation. I am completely unfamiliar with these, but they look like suitable 
tech for this discussion.

CPLDs are actually getting big enough to do the Commodore ASICs now, so that 
is another
option. CPLDs are fuse programmable, meaning the design stays until erased 
or reprogrammed.
Both use HDL (Hardware description languages...there are several the end JEDEC files are the only thing that counts.)

Many of the vendor programs include schematic entry, which may be easier if 
you are having trouble with learning the languages. I have heard in the past 
that this is buggy, but that was years ago and this may be much more stable 
by now.

Scott McDonnell 

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