Seagate Medalist ST31082A, Product Manual

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Chapter 6 Register Addresses and Functions
Page 42 ST3636A/ST31082A/ST31276A
Drive Address Register
Port Address: 3F7
Chip Select:
-HOST CS1
Register Address: 7
Function: Read only
Description: This register loops back the drive select and head select
addresses of the currently selected drive.
The bits in this register are as follows:
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
RSVD -WTG -HS3 -HS2 -HS1 -HS0 -DS1 -DS0
where:
• RSVD is reserved and negated by the drive. When the host reads the drive
address register, this bit must be in a high impedance state.
• -WTG is the write gate bit, which is active when writing to the disk drive is
in progress.
• -HS3 through -HS0 are the one’s complement of the binary coded address
of the currently-selected head. For example, if -HS3 through -HS0 are 1 1 0
0, respectively, head 3 is selected.
• -DS1 is the drive select bit for drive 1, and should be active when drive 1 is
selected and active.
• -DS0 is the drive select bit for drive 0, and should be active when drive 0 is
selected and active.
☞ ☞
Note: Bit 7 is not driven for compatibility with the floppy drive address space. If your system is
different, you may have to drive this bit when this register is read.
Command Register
Port Address: 1F7
Chip Select:
-HOST CS0
Register Address: 7
Function: Write only
Description: The eight-bit code written to this register passes the command
from the host to the drive. Command execution begins immediately after this
register is written.
Refer to chapter 7 for a list of executable commands with the command codes
and necessary parameters for each command.