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Be careful, there were typos in some versions of these tables. I
have attempted to correct those typos below. The notation (none,
none*, RDY, etc) are same as in the email previously posted here
(also reproduced below the tables).
The following table shows what ATA-1 through ATA/ATAPI-5 specify.
# dev0 SC SN CL CH ST ST2 dev1 SC SN CL CH ST ST2
a ata 01 01 00 00 00 RDY none* 01 01 00 00 00 00
b ata 01 01 00 00 00 RDY ata 01 01 00 00 00 RDY
c ata 01 01 00 00 00 RDY atapi 01 01 14 eb 00 00
d atapi 01 01 14 eb 00 00 none* 01 01 14 eb 00 00
e atapi 01 01 14 eb 00 00 ata 01 01 00 00 00 RDY
f atapi 01 01 14 eb 00 00 atapi 01 01 14 eb 00 00
g none ?? ?? ?? ?? ?? ?? none ?? ?? ?? ?? ?? ??
h none ?? ?? ?? ?? ?? ?? ata 01 01 00 00 00 RDY
i none ?? ?? ?? ?? ?? ?? atapi 01 01 14 eb 00 00
The following table is what ATA/ATAPI-6 currently specifies.
# dev0 SC SN CL CH ST ST2 dev1 SC SN CL CH ST ST2
a ata 01 01 00 00 00 RDY none* 01 01 00 00 00 00
b ata 01 01 00 00 00 RDY ata 01 01 00 00 00 RDY
c ata 01 01 00 00 00 RDY atapi 01 01 14 eb 00 00
d atapi 01 01 14 eb 00 00 none* 00 00 00 00 00 00
e atapi 01 01 14 eb 00 00 ata 01 01 00 00 00 RDY
f atapi 01 01 14 eb 00 00 atapi 01 01 14 eb 00 00
g none ?? ?? ?? ?? ?? ?? none ?? ?? ?? ?? ?? ??
h none ?? ?? ?? ?? ?? ?? ata 01 01 00 00 00 RDY
i none ?? ?? ?? ?? ?? ?? atapi 01 01 14 eb 00 00
Note that the only difference in the tables is in line d.
I still do not understand what value the ATA/ATAPI-6 change has
other than to greatly confuse all hardware, firmware and software
folks. The ATA/ATAPI-6 change does require hardware changes and
is a major change to something that goes back to ATA-1. To me
this is just another example of T13 changing things with little
regard for the true impact on the rest of the world.
Notation:
This table shows the signature values in SC, SN, CL and CH and
the status in ST at two times. The first status is right after
device 0 sets BSY=0. Now assume that if there are two ATA
devices, that those devices have basically the same spin up
times. Lets assume that is 10 seconds. So the table shows the
status a second time, labelled ST2, after the ATA spin up time.
So the ST and ST2 values are read by the host at least 10 seconds
apart. And be careful, issuing a command or a Soft Reset while
an ATA device has status of 00 does not change the state of DRDY.
'RDY' means the ATA device has set DRDY=1 so it probably has
status of 40 or 50.
'none*' means the register values are being supplied by device 0.
*** Hale Landis *** [EMAIL PROTECTED] ***
*** Niwot, CO USA *** www.ata-atapi.com ***
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