Andre Hedrick wrote:
>
> That is a legacy bit from ATA-2 but it is one of those things you can not
> get rid of :-( even thou things are obsoleted, they are not retired.
> This means that you have to go back into the past to see how it was used,
> silly! I hope you agree to that point.
No,
in ANSI X3.279-1996, "AT Attachment Interface with Extensions (ATA-2)",
Approved September 11, 1996 , control register bit 3-7 are reserved.
However ANSI X3.221-1994, "AT Attachment Interface for Disk Drives",
Approved May 12, 1994, bit3 is "1" and bits 4-7 are "x". No further explanation.
How far back must we go, to get the sense ?
>
> This is the drive->ctrl register pointer.
>
> outp(drive->ctl|0x02, IDE_CONTROL_REG);
>
> typedef union {
> unsigned all : 8; /* all of the bits together */
> struct {
> unsigned bit0 : 1;
> unsigned nIEN : 1; /* device INTRQ to host */
> unsigned SRST : 1; /* host soft reset bit */
> unsigned bit3 : 1; /* ATA-2 thingy */
> unsigned reserved456 : 3;
> unsigned HOB : 1; /* 48-bit address ordering */
> } b;
> } control_t;
>
> This is a new struct that is to be added for 48-bit addressing and it will
> reflect drive->ctl soon. I have not decided how to use it best or at all,
> but it has meaning and once I add-in the real def of bit3 then I will not
> need to look it up again.
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