Archived from groups: comp.sys.ibm.pc.hardware.storage (
More info?)
"J. Clarke" <jclarke@nospam.invalid> wrote in message news:ckg9vt01olu@news2.newsguy.com
> Ranga wrote:
>
> > Hi,
> >
> > Hard Disk has only three address lines. But the capacity of the Hard
> > disk seem to rise from few MB to 100, 200 GB.
> >
> > How will this happen?
If that 3 (actually it is 5) was enough for a few MB already, why would
there be a problem for bigger drives?
Obviously the device address select DA(0-2) lines are used for something
different.
5.2.1 CS(1:0)- (Chip select)
These are the chip select signals from the host used to select the Command
Block or Control Block registers (see 7.2). .
5.2.2 DA(2:0) (Device address)
This is the 3-bit binary coded address asserted by the host to access a
register or data port in the device (see 7.2).
> >
> > Can anyone explain or provide any reference sites for this?
ATA-ATAPI specs at www.t13.org
The references I gave are from (ATA/ATAPI-6) Rev. 3
>
> The address lines are used to determine which of several hard disks
> attached to a cable is being accessed,
Nonsense.
The socalled 3 'address' lines are used to select a register in both drives.
The DEV bit determines which drive will respond.
3.1.24 device selection: A device is selected when the DEV bit of the
Device register is equal to the device number assigned to the device by
means of a Device 0/Device 1 jumper or switch, or use of the CSEL signal.
> not to determine which location on the disk is to be accessed.
Sure it does.
> That information is passed down the data bus as a coded command.
Both are delivered that way.
> >
> > With Regards,
> > Ranga.