Command Protocol; Pio Data In Commands - IBM DTLA-305040 - Deskstar 41.1 GB Hard Drive Specifications

11.0 Command Protocol

The commands are grouped into different classes according to the protocols followed for command exe-
cution. The command classes with their associated protocols are defined below.
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 one to
zero during command execution.
A command shall only be interrupted with a hardware 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 com-
mand 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.
Figure 147 on page 0 shows the device time-out values.

11.1 PIO Data In commands

These commands are
Ÿ Identify Device
Ÿ Read Buffer
Ÿ Read Long
Ÿ Read Multiple
Ÿ Read Sectors
Ÿ SMART Read Attribute Values
Ÿ SMART Read Attribute Thresholds
Execution includes the transfer of one or more 512 byte (>512 bytes on Read Long) sectors of data from
the device to the host.
1. The host writes any required parameters to the Features, Sector Count, Sector Number, Cylinder,
and Device/Head Registers.
2. The host writes the command code to the Command Register.
3. For each sector of data to be transferred
a. The device sets BSY=1 and prepares for data transfer.
b. When a sector of data is available for transfer to the host, the device sets BSY=0, sets DRQ=1,
and interrupts the host.
c. In response to the interrupt the host reads the Status Register.
d. The device clears the interrupt in response to the Status Register being read.
Deskstar 40GV & 75GXP hard disk drive specifications
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