Specifications

i ATTO Technology Inc. ATTO ExpressSAS Host & RAID Adapter Installation and Operation Manual
Appendix A Glossary
Glossary
Some terms used in the SAS/SATA industry are defined below. More information is available through the
ATTO Technology website (
www.attotech.com ), or the Storage Area Networking Industry Association
( www.snia.org ).
Term Definition
ANSI American National Standards Institute
Auto Negotiation Hardware senses and automatically responds depending on configuration
Bit Smallest unit of data a computer can process: a single binary digit with a value of either 0 or 1
Bus A collection of unbroken signal lines used to transmit information from one part of a computer
system to another; taps on the lines connect devices to the bus
Byte An ordered set of 8 bits
CPU Central Processing Unit: the portion of the computer that actually performs computations
Device Driver A program that allows a microprocessor to direct the operation of a peripheral device
DMA Direct Memory Access: a way to move data from a storage device directly to RAM without using
the CPU’s resources
DMA bus master Allows a peripheral to control the flow of data to and from system memory by block as opposed to
allowing the processor to control the data by bytes (PIO or programmed I/O)
Host A processor, usually a CPU and memory, which communicates with devices over an interface
I2C (Inter-Integrated Circuit) is a multi-master serial single-ended computer bus that is used to attach
low-speed peripherals to a motherboard, backplane or embedded system
I 2 C Header I 2 C header is a connector on the adapter used to connect an I 2 C cable
LED Light-emitting diode: a type of diode that emits light when current passes through it; visible LEDs
are used as indicator lights on all sorts of electronic devices
Parity Checking A method which verifies the accuracy of data transmitted over the SCSI bus by adding one bit in
the transfer to make the sum of all the bits either odd or even (for odd or even parity); an error
message occurs if the sum is not correct
PCI Peripheral Component Interconnect. Allows peripherals to be connected directly to computer
memory, bypassing the slower ISA and EISA busses
PHY A physical connection between the adapter and a drive on the backplane. Each mini-SAS
connector carries signals for four phys
Port An access point in a device
Port Address Also port number; the address, assigned by the PCI bus, through which commands are sent to a
host adapter board
Port Number See port address
SCSI Small Computer Systems Interface: a processor-independent standard for system-level interface
between a computer and intelligent devices including hard disks, floppy disks, CD-ROM, printers,
scanners, etc.
SEP SCSI Enclosure Process. A SEP is a device, typically a backplane, that is capable of executing
SCSI SES commands
SES SCSI Enclosure Services. A SCSI specification that defines SCSI commands for controlling an
enclosure. These commands include the capability to control LED indicators on an enclosure