IBM IC25N020ATDA04 Hard Drive Specifications - Page 86

Alternate Status Register, 2 Command Register, 3 Cylinder High Register

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10.1 Alternate Status Register Alternate Status Register 7 6 5 4 3 2 1 0 BSY RDY DF DSC DRQ COR IDX ERR Figure 54. Alternate Status Register This register contains the same information as the Status Register. The only difference between this register and the Status Register is that reading the Alternate Status Register does not imply an interrupt acknowledge or a clear of a pending interrupt. See Section 10.12, "Status Register" on page 76 for the definition of the bits in this register. 10.2 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 73 on page 109. All other registers required for the command must be set up before writing to the Command Register. 10.3 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 be from zero to the number of cylinders minus one. 10.4 Cylinder Low Register This register contains the low order 8 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 (1). Travelstar 48GH, 30GN & 15GN hard disk drive specifications 72

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10.1 Alternate Status Register
0
ERR
1
IDX
2
COR
3
DRQ
4
DSC
5
DF
6
RDY
7
BSY
Alternate Status Register
Figure 54. Alternate Status Register
This register contains the same information as the Status Register. The only difference between this
register and the Status Register is that reading the Alternate Status Register does not imply an interrupt
acknowledge or a clear of a pending interrupt. See Section 10.12, "Status Register" on page 76 for the
definition of the bits in this register.
10.2 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 73 on page 109. All other
registers required for the command must be set up before writing to the Command Register.
10.3 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 be from zero to the number of cylinders minus one.
10.4 Cylinder Low Register
This register contains the low order 8 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 (1).
Travelstar 48GH, 30GN & 15GN hard disk drive specifications
72