Device/Head Register; Figure 56. Device/Head Register - IBM IC25N020ATDA04 - Travelstar 20 GB Hard Drive Specifications

10.7 Device/Head Register

Figure 56. Device/Head Register

This register contains the device and head numbers.
Bit Definitions
L
DRV
HS3,HS2,HS1,HS0
Device/Head Register
7 6 5
1 L 1
Binary encoded address mode select. When L = 0 , addressing is by CHS mode.
When L = 1, addressing is by LBA mode.
Device. When DRV = 0, device 0 (master) is selected. When DRV = 1, device 1
(Slave) is selected.
Head Select. These four bits indicate the binary encoded address of the head. Bit
HS0 is the least significant bit. At command completion, these bits are updated to
reflect the currently selected head. The head number may be from zero to the
number of heads minus one. In LBA mode, HS3 through HS0 contain bits 24–27
of the LBA. At command completion, these bits are updated to reflect the current
LBA bits 24–27.
Travelstar 48GH, 30GN & 15GN hard disk drive specifications
4 3 2
DRV HS3 HS2 HS1
74
1 0
HS0