This message is from the T13 list server.
Below I have provided what I think is more accurate and more
complete text for sections 4 and 5 of the e05104r0 proposal. See
my list of questions following my proposed text. I hope this
version helps everyone understand what is really being
proposed...
===begin
4 Description of the BSY=0 DRQ=1 ERR=1 Feature
Under this proposal a new Set Features function would allow a
device to conform to the PIO data-in and PIO data-out command
protocols as described by ATA-1 (withdrawn in 1999) and ATA-2
(withdrawn in 2001) standards.
This proposal also sets aside a supported and an enabled bit in
new Identify words allocated for feature support/enable
reporting.
5 BSY=0 DRQ=1 ERR=1 Function
During the processing of a PIO data-in or PIO data-out command a
device has status of BSY=0 DRQ=1 when the device is requesting
data transfer. The ATA-3, ATA/ATAPI-4, ATA/ATAPI-5, ATA/ATAPI-6
and ATA/ATAPI-7 standards prohibit the BSY=0 DRQ=1 ERR=1 status,
as does the Serial ATA Design Guide 21. However, ATA-1 and ATA-2
allowed, but did not require, status of BSY=0 DRQ=1 ERR=1 and
those standards describe how a host should respond to this device
status.
When this feature is supported and enabled a device is allowed to
use the ATA-1 and ATA-2 status of BSY=0 DRQ=1 ERR=1 during the
execution of PIO data-in and PIO data-out commands.
5.1 New SET FEATURE Subcommands
Table 1 - SET FEATURES subcommand definitions
Subcommand Action
5Fh Disable BSY=0 DRQ=1 ERR=1 status.
DFh Enable BSY=0 DRQ=1 ERR=1 status.
5.2 Enable/disable BSY=0 DRQ=1 ERR=1 feature
SET FEATURES subcommand codes 5Fh and DFh disable and enable
ATA-1/ATA-2 BSY=0 DRQ=1 ERR=1 status for PIO data-in and PIO
data-out commands.
If this feature is supported it shall be disabled at power on and
by Hardware Reset. The enabled or disabled state of this feature
shall not be changed by Software Reset. For Serial ATA devices
if this feature is supported it shall be disabled at all times.
6 New Identify Words 119-120
This proposal reserves words 119-120 for expansion of the feature
implemented/enabled words and defines a bit for the BSY=0 DRQ=1
ERR=1 feature.
The new words are shown in Table 2.
Table 2 - IDENTIFY DEVICE information
Word O/M F/V Bit(s) Description
86 F 15 Words 119-120 are valid
119 F 15-1 Reserved
F 0 1 = the BSY=0 DRQ=1 ERR=1 feature
is supported.
0 = the BSY=0 DRQ=1 ERR=1 feature
is not supported.
120 F 15-1 Reserved
V 0 1= the BSY=0 DRQ=1 ERR=1 feature
is enabled.
0= the BSY=0 DRQ=1 ERR=1 feature
is disabled.
Add to word 86:
If bit 15 of word 86 is set to 1 words 119-120 are valid.
6.1 Word 119 Features/command sets supported
Word 119 shall indicate features/command sets supported. If a
defined bit is cleared to zero, the indicated features/command
set is not supported.
If bit 0 of word 119 is set to one, the optional BSY=0 DRQ=1
ERR=1 feature is supported.
6.2 Word 120 Features/command sets enabled
Word 120 shall indicate features/command sets supported. If a
defined bit is cleared to zero, the indicated features/command
set is not enabled.
If bit 0 of word 120 is set to one, the BSY=0 DRQ=1 ERR=1 feature
is enabled.
===end
Questions about new words 119 and 120 in this proposal...
a) Why define new words for command/features? Are there no
unused bits in words 82-87? If there is a need for these new
ID words, that proposal should be separated from the BSY=0
DRQ=1 ERR=1 proposal.
b) Why do these new words have a different format from the other
supported/enabled words (82-87) that have specific values in
bits 15-14 to determine validity of the word's data?
c) If these new words are defined then why not define bits for
each of the features that exist (such as 8-bit data transfer,
read cache, etc)?
Hale
*** Hale Landis *** www.ata-atapi.com ***
