I don't think that is impossible because these kind of speech chips are (partly) analogue.....so I don't think an FPGA can fully "capture" a speech synth like that.
However it depends ons what the analogue parts are. If it's simply only a DAC or amplifier those could be done just outside the FPGA.
Somewhere above it was mentioned that they could emulate the SC-01-A very well because it was decapped. Decapping means that they removed the top of the chip (mechanically and/or chemically) to make lots of pictures of the chip through microscopes. That way, its becomes clear exactly how a chip was built-up.
Often manufacturers of course did not give away EXACTLY how their chips worked, mostly they only provided functional block diagrams (Atari was an exception, they actually included pictures of their dies (=chips) in the datasheets of f.i. ANTIC, GTIA and POKEY. Maybe they didn't provide the datasheets outside of the company or they didn't think anyone could reproduce them anyway (they also never thought any third parties would program for their 2600 in those early years).
The available copies of Atari's datasheets are so bad that you can't make anything of those pictures by the way.
Raspberry Pi would be emulation.
Edited by Level42, Fri Dec 8, 2017 1:55 AM.