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Date   : Fri, 29 Sep 2000 07:22:58 +0100
From   : Philip Peake <philipp@...>
Subject: Re: 1770 disc interface

Hi all,

Thanks for your answers Mike.
The 1770 daughter board was a circuit drawing project, but hasn't been updated
for
two years and the email address of Charlie Cole is not functioning (postmaster
bounceback).
I shall have to get a secondhand one to find out exactly what's on it. However,
they're not easy to find, I think I'll have to buy a whole 'new' computer to get
one!
The default step rate of the 1772 should be ok for a 3.5" drive though which
(with
ADFS) is what I want to connect.
Actually, both the 1770 and 1772 are ruddy hard to get hold of these days (it
would seem that the older 8271 is actually easier to find). One company has found
them for me, at a cost of £8.some, but I would have to buy 24! I'll keep looking.

Phil Peake



Mike Tomlinson wrote:

> In article <39CFA3C6.C63EE023@...>, Philip Peake <philipp@...>
> writes
> >Hi all,
> >
> >Does anyone have a circuit diagram for the 1770 disc interface?
>
> no, but have a look at the 1770 DFS upgrade kit fitting instructions at
> the doc project:
>
> http://members.magnet.at/marku/
>
> there is also a '1770 DFS daughter board' in progress.  Not sure what
> this is.
>
> > Has anyone tried
> >to build one (for the model B)?
>
> no, but it should be do-able.  Wouldn't it be easier to find a
> secondhand one?
>
> >Can one do a straight swap WD1770PH for WD1772PH?
>
> yes, but the step rates are different - Acorn did at one point change
> the 1770 chip on the BBC upgrade for a 1772. (The rom stayed the same.)
> The jumper links on the keyboard changed and the fitting instructions
> detailed what the links needed to be for both the 1770 and the 1772.
>
> Unfortunately, the copy of the instructions at the doc project don't
> include the addendum sheet for the 1772 and I can't find a copy of it.
> The default step rate for the 1770 was 6mS, on the 1772 with the default
> liks it's 3mS, which is too fast for 5.25" drives.
>
> > Also, does the
> >ADFS
> >rom require the DFS rom to be present to work?
>
> no
>
> > And can the rom images at
> >http://www.nvg.ntnu.no/bbc/roms/ be blown to PROM
>
> yes
>
> >As well as the 1770 module, the Acorn installation guide specifies that '2 off
> >7438 Integrated Circuits' are required for the 14 pin DIL sockets at IC79 and
> >IC80. Is the Texas Instruments SN7438N suitable for this?
>
> yes.  Do not use the 74LS38.
>
> --
> Mike Tomlinson
> mike@...
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