AT INTERFACE and ATA COMMANDS
6-
10 WA31273A / WA32543A / WA33203A / WA3216A / WA31083A / WA32162A
The physical sector address is made up of three fields: the sector number, the head
number and the cylinder number. Sectors are numbered from 0 to a device specific
maximum value which cannot exceed 255. Heads are numbered from 0 to a device
specific maximum value which cannot exceed 15. Cylinders are numbered from 0 to a
device specific maximum value which cannot exceed 65,535. Typically, sequential access
to the media is accomplished by treating the sector number as the least significant
portion, the head number as the mid-portion, and the cylinder number as the most
significant portion of the CHS address.
In LBA (Logical Block Address) mode the sectors on the device are assumed to be
linearly mapped with an Initial definition of : LBA 0 = (Cylinder 0, head 0, sector 0).
Irrespective of translate mode geometry set by the host, the LBA address of a given
sector does not change:
LBA = ((cylinder * heads_per_cy heads) * sectors_per_track) + sector - 1
6-3-2 I/O Register-Address
Communication to or from the drive is through an I/O Register that routes the input or
output data to or from registers addressed by a code on signals from the host (CS1FX-,
CS3FX-, DA2, DA1, DA0, DIOR- and DIOW-).
The Command Block Registers are used for sending commands to the drive or posting
status from the drive.
The Control Block Registers are used for drive control and to post alternate status. Table
6-3 lists these registers and the addresses that select them.
Table 6-3.
I/O Port Function/Selection Address
Address
Functions
CS1FX-
CS3FX-
DA2
DA1
DA0
READ(DIOR-)
WRITE(DIOW-)
Control Block Registers
N
N
X
X
X
High Impedance
Not Used
N
A
0
X
X
High Impedance
Not Used
N
A
1
0
X
High Impedance
Not Used
N
A
1
1
0
Alternate Status
Device Control
N
A
1
1
1
Device Address
Not Used
Command Block Registers
A
N
0
0
0
Data
Data
A
N
0
0
1
Error Register
Features
