SpinPoint Barracuda Series, Product Manual

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Barracuda Product Manual Rev04
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The only two register values used by this command are the Sector Count register which specifies the number
of sectors per track, and the Drive/Head register which specifies the number of heads minus 1. The sector
count and head values are not checked for validity by this command. If they are invalid, no error will be
posted until an illegal access is made by some other command.
8.2.11 NOP (00h)
The NOP command is always responded with command aborted.
8.2.12 Read Buffer (E4h)
The Read Buffer command enables the host to read the current contents of the drive's sector buffer. When
this command is issued, the drive sets up the sector buffer for a read operation, sets DRQ, clears BSY, and
generates an interrupt. The host then reads up to 512 bytes of data from the buffer.
The Read Buffer and Write Buffer commands are synchronized so that sequential Write Buffer (E8h) and
Read Buffer commands access the same 512 bytes within the buffer.
8.2.13 Read DMA (C8h, 25h: extended)
This command executes in a manner similar to the Read Sector(s) command except for the drive issues only
one interrupt per command to indicate that data transfer has stopped and the status is available.
Any unrecoverable error encountered during execution of a Read DMA command results in the termination
of data transfer prior to the sector where the error was detected. The drive generates an interrupt to indicate
that data transfer has terminated and status is available. The error posting is the same as that for the Read
Sector(s) command.
8.2.14 Read FPDMA Queued (60h)
This command is implemented according to the Serial ATA II: Extension to Serial ATA 1.0a, Revision 1.2
specification. The purpose of this command is for the host to issue a Native Command Queue (NCQ) read
commands. This command allows device to reorder the command issued in a sequence of the queue. The
command is returned based on the device’s determine of the location sequence.
The Barracuda drive implemented a queue depth of 32. This will allow host to issue up to 32 NCQ
commands (combined read and write commands).
If the drive enters NCQ mode and a non-queue command is received, the drive will respond with error to
inform host a queue command been overlapped with non-queue. If a queue tag is not finished and another
same tag command is received, the drive will response with error to inform host a duplicated tag is received.
Error information is reported according to the SATA II specification. A read Log Extended command with
log page 10 is required to retrieve the error information
.