Date   : Fri, 26 Nov 2010 02:34:02 +0000
From   : jgh@... (J.G.Harston)
Subject: Electron Ferranti ULA reverse engineering progress

James McGill wrote:
> I don't suppose you know of any resources for the BBC's 1200 baud
> cassette interface? My best guess is that the analog cassette signal
> is quantized to a digital signal and then processed in software

It's all processed in hardware, the software meerly reads/writes to
the 6850 ACIA. The signals to/from the ACIA are converted to/from
cassette signals by the serial ULA.

See the circuit diagram here:
http://mdfs.net/Info/Comp/BBC/Circuits/bbc.gif

-- 
J.G.Harston - jgh@...