IBM IC35L020 - Deskstar 20 GB Hard Drive - Alternate Status Register; Command Register; Cylinder High Register; Cylinder Low Register

12.1 Alternate Status Register
ERRIDXCORDBQ
DSC/
SERV
DFRDYBSY
01234567
Alternate Status Register
Figure 59. Alternate Status Register
This register contains the same information as the Status Register. The only difference is that reading
this register does not imply interrupt acknowledge or clear a pending interrupt. See Section 12.13,
"Status Register" on page 72 for the definition of the bits in this register.
12.2 Command Register
This register contains the command code being sent to the device. Command execution begins
immediately after this register is written. The command set is shown in Figure 76 on pages 101 and 102.
All other registers required for the command must be set up before writing the Command Register.
12.3 Cylinder High Register
This register contains the high order bits of the starting cylinder address for any disk access. At the end
of the command this register is updated to reflect the current cylinder number.
In LBA Mode this register contains Bits 16–23. At the end of the command this register is updated to
reflect the current LBA Bits 16–23.
The cylinder number may range from zero to the number of cylinders minus one.
12.4 Cylinder Low Register
This register contains the low order bits of the starting cylinder address for any disk access. At the end of
the command this register is updated to reflect the current cylinder number.
In LBA Mode this register contains Bits 8–15. At the end of the command this register is updated to
reflect the current LBA Bits 8–15.
The cylinder number may be from zero to the number of cylinders minus one.
Deskstar 60 GXP Hard disk drive specification
68