ESDI drives

From: Don Maslin <donm_at_cts.com>
Date: Sun Apr 8 00:53:28 2001

On Sat, 7 Apr 2001, Tony Duell wrote:

> >
> > Tony is (almost) correct: ESDI drives use a binary select scheme similar to
> > SCSI. The three select bits are decoded to enable drives 1,2,...,6,7.
> > There's no "drive 0" because that corresponds to the "deselect all drives"
> > condition.
>
> Oh, right. I wondered if it did... Incidentally, is the ESDI spec
> available anywere (or at least a signal description)?

To what level of detail, Tony? I have a copy of the Maxtor Product Spec
and OEM Tech Manual for the XT-8000E/EH drives that I can extract some
information from.
                                                 - don
 
> > However, some PC controllers only support two drives (another legacy of the
> > IBM PC BIOS) and of course they use drives 1 and 2. Therefore, some PC
> > manufacturers suggest using a cable with a twist, to swap pins 26 and 28
> > (DS1 and DS2), leaving the select jumpers the same on both drives. I've
> > never seen a cable with a twist on a "real" ESDI system.
>
> I wondered about that, too (it was an obvious way for a twist to be able
> to swap drives 1 and 2). I assume from this that the drive select lines
> are not used as data lines for anything else, then (unlike SCSI, say,
> where the same 8 lines are used both to select a particular unit and to
> transfer commands and data).
>
> -tony
>
Received on Sun Apr 08 2001 - 00:53:28 BST