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DISK DRIVE OPERATION
SpinPoint V40 Product Manual
83
6.6 Protocol Overview
Commands can be grouped into different classes according to the protocols followed for command execution.
The command classes with their associated protocols are defined below.
For all commands, the host first checks if BSY=1, and should proceed no further unless and until BSY=0.
For most commands, the host will also wait for DRDY=1 before proceeding. Those commands shown with
DRDY=X can be executed when DRDY=0.
6.6.1 PIO Data in Commands
This class includes:
• Identify Drive (ECh)
• Read Buffer (E4h)
• Read Long (22h)
• Read Multiple (C4h)
• Read Sector(s) (20h)
• SMART Read Data
• SMART Read Log Sector
Execution includes the transfer of one or more 512 byte (>512 bytes on Read Long) sectors of data from the
drive to the host.
a) The host writes any required parameters to the Features, Sector Count, Sector Number, Cylinder and
Drive/Head registers.
b) The host writes the command code to the Command register.
c) The drive sets BSY and prepares for data transfer.
d) When a sector of data is available, the drive sets DRQ and clears BSY prior to asserting INTRQ.
e) After detecting INTRQ, the host reads the Status register, then reads on sector of data via the Data
register. In response to the Status register being read, the drive negates INTRQ.
f) The drive clears DRQ. If transfer of another sector is required, the drive also sets BSY and the above
sequence is repeated from (d).