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Western Digital Hard Disk Drive OEM Specification
10
Command Protocol
The commands are grouped into different classes according to the protocols followed for command execution. The
command classes with their associated protocols are defined below.
Please refer to Serial ATA Revision 3.2 about each protocol.
For all commands, the host must first check if BSY=1, and should proceed no further unless and until BSY=0. For all
commands, the host must also wait for RDY=1 before proceeding.
A device must maintain either BSY=1 or DRQ=1 at all times until the command is completed. The INTRQ signal is
used by the device to signal most, but not all, times when the BSY bit is changed from 1 to 0 during command
execution.
A command shall only be interrupted with a COMRESET or software reset. The result of writing to the Command
register while BSY=1 or DRQ=1 is unpredictable and may result in data corruption. A command should only be
interrupted by a reset at times when the host thinks there may be a problem, such as a device that is no longer
responding.
Interrupts are cleared when the host reads the Status Register, issues a reset, or writes to the Command Register.
10.1
PIO Data In commands
These commands are:
Device Configuration Identify
Identify Device
Read Buffer
Read Log Ext
Read Multiple
Read Multiple Ext
Read Sector(s)
Read Sector(s) Ext
Read Stream Ext
SMART Read Attribute Values
SMART Read Attribute Thresholds
SMART Read Log Sector
Trusted Receive
Execution includes the transfer of one or more 512 byte sectors of data from the device to the host.
10.2
PIO Data Out commands
These commands are:
Device Configuration Set
Download Microcode
Format Track
Security Disable Password
Security Erase Unit
Security Set Password
Security Unlock
Set Max Set Password command
Set Max Unlock command
SMART Write Log Sector
Trusted Send
Write Buffer
