Date   : Thu, 23 Nov 2006 14:05:19 +0000
From   : pete@... (Pete Turnbull)
Subject: BBC Disk Drive?

On 23/11/2006 12:10, Richard Gellman wrote:

> Is this a D-type connector (a la the analogue port)? If so it could an
> Amiga-type floppy disk interface. It would be the first time I've seen
> such a thing used in the context of a BBC micro though.
> 
> The Amiga has an external floppy port that uses 37-way D connector. If it
> is said interface, then you can build an adapter as I believe the signal
> set is the same.

All the Amiga external drive connectors I've seen are 23-pin D 
connectors (a non-standard size) though the signals are basically the 
same set as on a normal floppy -- albeit in a slightly different order.

I think you're mis-remembering this or confusing it with the original 
IBM PC floppy interface, which had a DC37 connector for an external 
drive (or two), and is virtually the same as the FTAPE interface 
sometimes found on multi-IO ISA cards for tape backup.

The pinout for the DC37 is so close to the normal interface that you can 
just crimp a ribbon cable onto the connectors in the usual way; pins 1-4 
on the DC37 are the four pins normally found on the power connector, pin 
5 is sometimes a head-load signal, and pins 6-19 correspond to the 
uppermost 14 signals on the normal 34-way connector (pins 
8,10,12,...34).  The other 3 signals (Density Select on pin 2, In Use on 
pin 4, and Drive Select 3 (counting DS0, DS1, DS2, DS3) are neither 
needed nor used on a Beeb.  Note that the pins on a DC37 are numbered 
from 1 to 19 along one side and 20 to 37 along the other side, whereas 
the pins on the 34-way edge connector or header are numbered with all 
the odd numbers on one side and all the even ones on the other side. 
All the odd-numbered pins on the 34-way connector, and the corresponding 
pins on the DC37, are grounded.

> Is the socket fitted to the casing of the drive unit, or to the drive
> circuit board? If the former, you may find the traditional edge connector
> inside to which you can attach a standard BBC floppy cable.

Indeed, that's what I'd expect, too.


-- 

Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York