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Barracuda Serial ATA V Product Manual, Rev. B 1
1.0 Introduction
This manual describes the functional, mechanical and interface specifica-
tions for ST3120023AS, ST380023AS, and ST360015AS serial ATA inter-
face drives.
1.1 About the serial ATA interface
The serial ATA interface provides several advantages over the traditional
(parallel) ATA interface. The primary advantages include:
• Easy installation and configuration with true plug-and-play connectivity. It
is not necessary to set any jumpers or other configuration options.
• Thinner and more flexible cabling for improved enclosure airflow and ease
of installation.
• Scalability to higher performance levels.
In addition, serial ATA makes the transition from parallel ATA easy by provid-
ing legacy software support. Serial ATA was designed to allow you to install a
serial ATA host adapter and serial ATA disc drive in your current system and
expect all of your existing applications to work as normal.
The serial ATA interface connects each disc drive in a point-to-point configu-
ration with the serial ATA host adapter. There is no master/slave relationship
with serial ATA devices like there is with parallel ATA. If two drives are
attached on one serial ATA host adapter, the host operating system views the
two devices as if they were both “masters” on two separate ports. This
essentially means both drives behave as if they are Device 0 (master)
devices.
Note. The host adapter may, optionally, emulate a master/slave environ-
ment to host software where two devices on separate serial ATA
ports are represented to host software as a Device 0 (master) and
Device 1 (slave) accessed at the same set of host bus addresses. A
host adapter that emulates a master/slave environment manages
two sets of shadow registers. This is not a typical serial ATA environ-
ment.
The serial ATA host adapter and drive share the function of emulating parallel
ATA device behavior to provide backward compatibility with existing host sys-
tems and software. The Command and Control Block registers, PIO and
DMA data transfers, resets, and interrupts are all emulated.
The serial ATA host adapter contains a set of registers that shadow the con-
tents of the traditional device registers, referred to as the Shadow Register
Block. All serial ATA devices behave like Device 0 devices. For additional