This message is from the T13 list server.
And MANY do not do anything with the upper bits.....
Therefore the host software MUST mask off the upper bits on read,
And the drive must mask off the upper bits on a write.
In case of the status Byte mask all other bits when checking for BSY
(i.e. if the BSY bit is high, All the other bits of the byte (D6:D0) are
indeterminate.
Jeff
Jeff Wolford Email: [EMAIL PROTECTED]
Master Architect
Storage Interface and Tools - Business PC Group
Voice: (281) 514-9465, Pager: (800) 973-5739
Hewlett-Packard Corporation
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
> Behalf Of Hale Landis
> Sent: Friday, September 10, 2004 9:28 AM
> To: [EMAIL PROTECTED]; [EMAIL PROTECTED]
> Subject: Re: [t13] Who Should Drive DD[15:8] during register reads ?
>
> This message is from the T13 list server.
>
>
> On Fri, 10 Sep 2004 21:39:53 +0900, [EMAIL PROTECTED]
> wrote:
> >This message is from the T13 list server.
> >(1) No one should drive DD15-8 during register reads.
> >(2) Many host systems pull the ATA DDx signals high.
> >None of this is in the standard document, but...
> >If (1) is true, shouldn't it be MANDATORY for the host to
> pull up the
> >DD15-8 ?
>
> This is a design issue for the host system. The host system
> could pull DDx up or down - that has no effect on how the ATA
> interface operates (the DDx signals are Tri-State). This is
> much like the INTRQ signal - some hosts pull it high, some
> hosts pull it low - some hosts are level triggered and some
> are edge triggered - none of this effects how the ATA
> interface operates - these are just internal host design issues.
>
> Hale
>
>
> *** Hale Landis *** www.ata-atapi.com ***
>
>
>
>
