Seagate Medalist ST31082A, Product Manual

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Chapter 6 Register Addresses and Functions
Page 38 ST3636A/ST31082A/ST31276A
Device/Head Register
Port Address: 1F6
Chip Select:
-HOST CS0
Register Address: 6
Function: Read/Write
Description: This register contains the drive and head numbers, as defined
below:
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
1 LBA 1 DRV HEAD
where:
• DRV is the binary encoded drive select number. When this bit is reset,
the master drive is selected, and when this bit is set, the slave drive is
selected. While both drive’s Task File registers are always written, this
bit selects which drive will respond and execute a command.
• LBA is the binary coded address mode select. When L = 0, addressing is
by CHS mode. When L = 1, addressing is by LBA mode. This bit was
RSVD (reserved) for use by the host and set to 0 prior to introduction of
LBA.
• HEAD
CHS Description: This is the four-bit binary encoded head select
number.
LBA Description: This register contains bits 24-27 of the logical block
address.
At the completion of each sector and at the end of the command, this register is
updated to reflect the currently selected head.