Seagate Surveillance HDD Product Manual, Rev. A
3
www.seagate.com
Introduction
1.1
About the SATA interface
The Serial ATA (SATA) 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, SATA makes the transition from parallel ATA easy by providing legacy software support. SATA was
designed to allow users to install a SATA host adapter and SATA disk drive in the current system and expect all of
the existing applications to work as normal.
The SATA interface connects each disk drive in a point-to-point configuration with the SATA host adapter. There is
no master/slave relationship with SATA devices like there is with parallel ATA. If two drives are attached on one
SATA 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.
The SATA host adapter and drive share the function of emulating parallel ATA device behavior to provide
backward compatibility with existing host systems and software. The Command and Control Block registers, PIO
and DMA data transfers, resets, and interrupts are all emulated.
The SATA host adapter contains a set of registers that shadow the contents of the traditional device registers,
referred to as the Shadow Register Block. All SATA devices behave like Device 0 devices. For additional
information about how SATA emulates parallel ATA, refer to the “Serial ATA International Organization: Serial ATA
Revision 3.0”. The specification can be downloaded from www.sata-io.org.
Note
The host adapter may, optionally, emulate a master/slave environment to host software where two devices on
separate SATA 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 SATA environment.
