Re: 6502 VHDL core?

From: Rainer Buchty (
Date: 2006-03-01 13:46:05

>Then there are also FPAAs which are FPGAs analog counterpart, good for
>SID filter creation or VIC video creation.

Actually, no. It would be completely nonsensical to use FPAAs for that. 
The FPAAs I've looked at were little more than programmable gain cells, 
so you could program some arbitrary, low level amplification and/or 
filtering, but that's about it.

Any native OTA-based design is more flexible, and, for that matter, way
more economical. That is why FPAAs have pretty much vanished from the
market -- and I doubt that they will ever come back.

Unlike logic equations, which you can map cheaply to lookup tables, 
storage elements, and routing, you can't really do a universal analog 
"FPGA" which would e.g. require to have programmable capacitors and 
resistors for instance.

With the advent of enough computing power to do all in the digital 
domain, there's also no need for going analog anymore, check out 
software-defined radio for instance.

>CPLDs are fuse programmable

No, otherwise they wouldn't be reprogrammable anymore :)

But they are manufactured in EEPROM or Flash technologies instead of 

>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.

Noone is doing schematic entry anymore apart from maybe showing
high-level connections between "black boxes". It's usually taking too
much time, plus it also leads the designer to adopt "dirty" tricks from
ancient time like building delays with a series of buffers/inverters.

In addition, it doesn't really make sense to e.g. build some decoder 
circuit, state machines etc. the hard way by using many 74xx. Any VHDL 
or Verilog code would be way more readable and understandable in that 


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