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On Wed, 11 Jul 2001 15:59:22 -0700, Eschmann, Michael K wrote:
>What I believe you may be seeing is the device selection delay problem,
>where you must wait 400nS for the device to have it's registers valid before
>you can read them. You may be getting the first device's status, then you
>read status again and get the newly-selected device's status. Please verify
>you are waiting 400nS or more before reading status.
What I have seen is devices that just toggle BSY for no apparently
good reason.
>This could be a case that device selection causes the drive in question to
>go busy until it can get it's state machine in order because it cannot be
>ready in 400nS. I've seen this in the past, but cannot enumerate/name the
>device for you (losing my memory, me thinks!)
But even setting BSY=1 because the DEV bit changed value is
absolutely and completely illegal. But I hear rumors there is some
ATAPI interface chip core floating around the Far East that does
this.
As I said before, devices that do this sort of stuff should never
pass any device evaluation test and should never be seen in computers
from well known system vendors. All these problems with ATAPI devices
go back to the failure of the systems manufacturers to require
confomance to the published standards for ATAPI devices. Anyone
building an ATA device that did this sort of stuff would sell zero
devices but for some reason the ATAPI device designers can just do
anything they want in violation of the published standards and they
will have no trouble selling their crappy devices. What gives?
*** Hale Landis *** [EMAIL PROTECTED] ***
*** Niwot, CO USA *** www.ata-atapi.com ***
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