Drive Address Register; Device/Head Register; Figure 53. Drive Address Register; Figure 54. Device/Head Register - IBM IC25N040ATCS04 - Travelstar 40 GB Hard Drive Specifications

10.7 Drive Address Register

Figure 53. Drive Address Register

This register contains the inverted drive select and head select addresses of the currently selected drive.
Bit Definitions
HIZ High Impedance. This bit is not a device and will always be in a high impedance
state.
-WTG -Write Gate. This bit is 0 when writing to the disk device is in progress.
-H3, -H2, -H1, -H0 -Head Select. These four bits are the one's complement of the binary coded
address of the currently selected head. Bit -H0 is the least significant.
-DS1 -Drive Select 1. The Drive Select bit for device 1 is active low. DS1 = 0 when
device 1 (slave) is selected and active.
-DS0 -Drive Select 0. The Drive Select bit for device 0 is active low. DS0 = 0 when device
0 (master) is selected and active.

10.8 Device/Head Register

Figure 54. Device/Head Register

This register contains the device and head numbers.
Bit Definitions
L Binary encoded address mode select. When L = 0, addressing is by CHS mode.
When L = 1, addressing is by LBA mode.
DRV Device. When DRV = 0, device 0 (master) is selected. When DRV = 1, device 1
(Slave) is selected.
HS3, HS2, HS0 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.
Drive Address Register
7 6 5
HIZ -WTG -H3
Device/Head Register
7 6 5
1 L 1
Travelstar 60GH & 40GN hard disk drive specifications
4 3 2
-H2 -H1 -H0 -DS1
4 3 2
DRV HS3 HS2
70
1 0
-DS0
1 0
HS1 HS0