Date   : Sat, 02 Jun 2001 10:28:33 -0700 (PDT)
From   : Thomas Harte <T.Harte@...>
Subject: Re: 1770 FDC and the Model B

>  Note: the bits of the BBC, B+ (maybe same as B, can't remember), Master
>  and Electron control registers are different.

There's a document on 'The BBC Lives!' or somewhere like that that
demonstrates the layout across these forms (I have it at home on my hard
disc if it can't otherwise be found) but I'm fairly sure of this - the B and
B+ bit configurations are seperate, and I know this for sure - the B+ and
Electron configurations are the same. Except that the B+ has a bit which may
or may not (the original source isn't sure) enable interrupts from the
WD1770, whereas on the Electron the WD1770 can never generate interrupts, so
that bit isn't important.

Also, for finding out how the 1770 actually works, rather than the
'reference' documents the BBC sites seem to carry, I found the Commodore
repositories most useful.

-Thomas





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