Communication Interfaces

Communication Interfaces

Listed below are commonly used Communication Interfaces. 


The different types of disk drive bus interface types are listed below. Keep in mind that Parallel ATA [PATA], Bus is being replaced by the Serial ATA [SATA] bus. SATA drives are available with capacities up to 500GB.

Internal Communicaion


PATA: Advanced Technology Attachment (ATA)
With the market introduction of Serial ATA in 2003, the original ATA was retroactively renamed Parallel ATA (PATA). In line with the original naming, this article only covers Parallel ATA. Many terms and synonyms for ATA exist, including abbreviations such as IDE, ATAPI, and UDMA.

ABC ATA-1 (IDE), [Obsolete] 8.3MBytes/sec, 8 or 16 bit data width, 40 pin data ribbon cable/connector. With a maximum of 2 devices on the bus. Using PIO Modes 0, 1 or 2. Performed no bus error correction. The ATA-1 specification was released in 1994, and was withdrawn in 1999.

ATA-2 (EIDE, or Fast ATA), [Obsolete] 16.6MBytes/sec, 8 or 16 bit data width, 40 pin data ribbon cable/connector. With a maximum of 4 devices on the bus. Using PIO Modes 0, 1, 2, 3, or 4. The ATA-2 specification was released in 1995 and was withdrawn in 2001.

ATA-3, 16MBytes/sec, 16 bit data width, 40 pin data ribbon cable/connector. Using PIO Modes 0, 1, 2, 3, or 4 and Multiword DMA modes 1 and 2. Runs with 120nS Strobes (rising edge to rising edge). Includes CRC. ATAPI (ATA Packet Interface)is the CD-ROM side of the interface. It uses the same connector as ATA, and adds 1 for analog and 1 for digital audio. The ATA-3 specification was released in 1997 and was withdrawn in 2002.

ATA-4 (Ultra-ATA/33), 33MBytes/sec, 16 bit data width, 40 pin data ribbon cable/connector. Using PIO Modes 0, 1, 2, 3, or 4 and Multiword DMA modes 1 and 2 and Ultra DMA modes 0, 1, and 2. Runs with 120nS Strobes (rising edge to rising edge), but used both edges of the Strobe producing an effective 60nS Strobe rate. 33MBps Transfer speed. Where 120nS cycle time is 4 clock periods at 30nS each. Added CRC checking. The ATA-4 standard was released in 1998.

ATA-5 (Ultra-ATA/66), 66MBytes/sec, 16 bit data width 40 pin data connector/80 pin cable, with the additional 40 new pins being Ground. The new cable allows ATA/66 to run at a faster rate then ATA/33. Using PIO Modes 0, 1, 2, 3, or 4 and Multiword DMA modes 1 and 2 and Ultra DMA modes 0, 1, 2, 3 and 4. Runs with 60nS Strobes (rising edge to rising edge), but uses both edges of the Strobe producing an effective 30nS Strobe rate. 66MBps Transfer speed. Where 60nS cycle time is 2 clock periods at 30nS each. The ATA-5 standard was released in 2000.

ATA-6 (Ultra-ATA/100), 100MBytes/sec,16 bit data width 40 pin data connector/80 pin cable, with the additional 40 new pins being Ground. Using PIO Modes 0, 1, 2, 3, or 4 and Multiword DMA modes 1 and 2 and Ultra DMA modes 0, 1, 2, 3, 4 and 5. 100MBps Transfer speed. Where 40nS cycle time is 2 clock periods at 20nS each. The ATA-6 standard was released in 2002.

ATA-7 (Ultra-ATA/133), 133MBytes/sec,16 bit data width 40 pin data connector/80 pin cable, with the additional 40 new pins being Ground. Using PIO Modes 0, 1, 2, 3, or 4 and Multiword DMA modes 0, 1 and 2 and Ultra DMA modes 0, 1, 2, 3, 4, 5 and 6. 133MBps Transfer speed. Where 30nS cycle time is 2 clock periods at 15nS each. The ATA-7 standard was released in 2005. With the introduction of Serial ATA, this is the last expected update of the IDE [PATA] bus. SATA: is faster, and requires a smaller cable, which means better air flow in the Chassis.

SATA: Serial ATA
SATA/150 (SATA 1.5Gb/s) runs at 1.5 Gigahertz (GHz). Serial ATA uses 8B/10B encoding at the physical layer. This encoding scheme has an efficiency of 80%, resulting in an actual data transfer rate of 1.2 Gigabits per second (Gb/s), or 150 megabytes per second (MB/s).

SATA/300 (SATA 3Gb/s) also referred to as SATA II. A 3Gb/s signalling rate was added to the PHY layer, offering up to twice the data throughput. To ensure seamless backward compatibility between older SATA and the newer faster SATA/3Gbs devices, the latter devices are required to support the original 1.5Gb/s rate. In practice, some older SATA systems that do not support SATA speed negotiation require the peripheral drive’s speed be manually hardlimited to 150 MB/s with the use of a jumper for a 300 MB/s drive.

SATA/600 (SATA 6Gb/s) The SATA-IO standards group plans to further increase the maximum throughput of Serial ATA to 600 MB/s around the year 2007.

SCSI: Small Computer System Interface


External Communicaion

Firewire: (also known as i.Link or IEEE 1394) – FireWire can connect together up to 63 peripherals in an acyclic topology. It allows peer-to-peer device communication. FireWire also supports multiple hosts per bus. It is designed to support Plug-and-play and hot swapping. It’s six-wire cable is more flexible then most Parallel SCSI cables and can supply up to 45 watts of power per port at up to 30 volts. FireWire 400 can transfer data between devices at 100, 200, or 400 Mbit/s data rates.
FireWire 800 (Apple’s name for the 9-pin “S800 bilingual” version of the IEEE1394b standard) was introduced commercially by Apple in 2003. This newer 1394 specification and corresponding products allow a transfer rate of 786.432  Mbit/s with backwards compatibility to the slower rates and 6-pin connectors of FireWire 400.

Universal Serial Bus (USB): A USB system has an asymmetric design, consisting of a host controller and multiple daisy-chained devices. Additional USB hubs may be included in the chain, allowing branching into a tree structure, subject to a limit of 5 levels of branching per controller (with no more than 127 devices). USB cables do not need to be terminated. The USB specification provides a 5 V supply on a single wire from which connected USB devices may draw power. The specification allows no more than 5.25 V and no less than 4.375 V. USB 1.0/1.1 supports two data transfer rates: Low Speed at 1.5 Mbit/s (183 KiB/s) and Full Speed at 12 Mbit/s.
USB 2.0: Released in April 2000, revised in December 2002. USB 2.0 Hi-Speed mode is 480 megabits per second.

USB 3.0 is the second major revision of the Universal Serial Bus (USB) standard for computer connectivity. First introduced in 2008, USB 3.0 adds a new transfer mode called “SuperSpeed,” (distinguishable from USB 2.0 by either the blue color of the port or the initials SS) capable of transferring data at up to 5 Gbit/s – more than ten times as fast as the 480 Mbit/s top speed of USB 2.0.