 | This article needs additional citations for verification .(July 2022) |
The Fibre Channel electrical interface is one of two related Fibre Channel standards that can be used to physically interconnect computer devices. The other standard is a Fibre Channel optical interface, which is not covered in this article.
Fibre channel electrical signals are sent over a duplex differential interface. This usually consists of twisted-pair cables with a nominal impedance of 75 ohms (single-ended) or 150 ohms (differential). This is a genuine differential signalling system so no ground reference is carried through the cable, except for the shield. Signalling is AC-coupled, with the series capacitors located at the transmitter end of the link.
The definition of the Fibre Channel signalling voltage is complex. Eye-diagrams are defined for both the transmitter and receiver. There are many eye-diagram parameters which must all be met to be compliant with the standard. In simple terms, the transmitter circuit must output a signal with a minimum of 600 mV peak-to-peak differential, maximum 2000 mV peak-to-peak differential. A good signal looks rather like a sine-wave with a fundamental frequency of half the data rate, so 1 GHz for a typical system running at 2 gigabits per second.
The Bit-Error Rate (BER) objective for Fibre Channel systems is 1 in 1012 (1 bit in 1,000,000,000,000 bits). At 2 Gbit/s this equates to seven errors per hour. Therefore, this is a common event and the receiver circuitry must contain error-handling logic. In order to achieve such a low error-rate, jitter "budgets" are defined for the transmitter and cables.
There are various Fibre Channel connectors in use in the computer industry. Details of their pinouts are distributed between different official documents. The following sections describe the most common Fibre Channel pinouts with some comments about the purpose of their electrical signals.
The most familiar Fibre Channel connectors are cable connectors, used for interconnects between initiators and targets (usually disk enclosures). There are also "device connectors" that can be found on Fibre Channel disk-drives and backplanes of enclosures. The device connectors include pins for power and for setting disk options.
| Pin | Signal name | Comments |
|---|---|---|
| 1 | +OUT | Fibre channel output |
| 2 | +5V | Optional |
| 3 | Module Fault Detect | Optional |
| 4 | Reserved | |
| 5 | +IN | Fibre channel input |
| 6 | -OUT | Fibre channel output |
| 7 | Output Disable | Optional |
| 8 | GND | Optional, return for pin 2 |
| 9 | -IN | Fibre channel input |
Optional pins 2, 3, 7, and 8 are intended for use with an external optical converter. This is often called a Media Interface Assembly (MIA).
Fibre channel DE-9 connectors often have only the 4 required contacts installed. Note that they are the four outermost contacts i.e. the same as used for Token Ring, this is an easy way to tell a fibre channel cable from an RS-232 cable.
| Pin | Signal name | Comments |
|---|---|---|
| 1 | +OUT | Fibre channel output |
| 2 | GND | Optional, return for pin 7 |
| 3 | -OUT | Fibre channel output |
| 4 | Module Fault Detect | Optional |
| 5 | Output Disable | Optional |
| 6 | -IN | Fibre channel input |
| 7 | +5V | Optional |
| 8 | +IN | Fibre channel input |
Optional pins 2, 4, 5, and 7 are intended for use with an external optical converter. This is often called a Media Interface Assembly (MIA).
| Pin | Signal name | Comments |
|---|---|---|
| 1 | GND | |
| 2 | -OUT | Fibre channel output |
| 3 | +OUT | Fibre channel output |
| 4 | GND | |
| 5 | +IN | Fibre channel input |
| 6 | -IN | Fibre channel input |
| 7 | GND | |
Although SCA-2 is the official name for this connector, it is often called SCA-40 to distinguish it by its pin count from other similar connectors.
| Pin | Signal name | Comments |
|---|---|---|
| 1 | -EN Bypass Port 1 | Output driven high when port 1 is operating correctly |
| 2 | +12V | |
| 3 | +12V | |
| 4 | +12V | |
| 5 | -Parallel ESI | Input to allow ESI operation using the SELx pins |
| 6 | -Drive Present | |
| 7 | ACTLED | Output to drive the activity LED cathode |
| 8 | Power Control | |
| 9 | START1 | Input to control spin-up behavior (see the Disk options section) |
| 10 | START2 | Input to control spin-up behavior (see the Disk options section) |
| 11 | -EN Bypass Port 2 | Output driven high when port 2 is operating correctly |
| 12 | SEL6 | Device ID bit 6 / ESI write clock |
| 13 | SEL5 | Device ID bit 5 / ESI read clock |
| 14 | SEL4 | Device ID bit 4 / ESI acknowledge clock |
| 15 | SEL3 | Device ID bit 3 / ESI bit 3 |
| 16 | FLTLED | Output to drive the fault LED cathode |
| 17 | DEVCTRL2 | Input to control interface speed (see the Disk options section) |
| 18 | DEVCTRL1 | Input to control interface speed (see the Disk options section) |
| 19 | +5V | |
| 20 | +5V | |
| 21 | +12V Charge | |
| 22 | GND (12V) | |
| 23 | GND (12V) | |
| 24 | +IN1 | Fibre channel input |
| 25 | -IN1 | Fibre channel input |
| 26 | GND (12V) | |
| 27 | +IN2 | Fibre channel input |
| 28 | -IN2 | Fibre channel input |
| 29 | GND (12V) | |
| 30 | +OUT1 | Fibre channel output |
| 31 | -OUT1 | Fibre channel output |
| 32 | GND (5V) | |
| 33 | +OUT2 | Fibre channel output |
| 34 | -OUT2 | Fibre channel output |
| 35 | GND (5V) | |
| 36 | SEL2 | Device ID bit 2 / ESI bit 2 |
| 37 | SEL1 | Device ID bit 1 / ESI bit 1 |
| 38 | SEL0 | Device ID bit 0 / ESI bit 0 |
| 39 | DEVCTRL0 | Input to control interface speed (see the Disk options section) |
| 40 | +5V CHARGE | |
Some of the input signals to a Fibre Channel disk are used to control options, as follows:
START options - if all the disks in an enclosure spin-up immediately on power-on, this can overload the power-supply. Two methods are available to avoid that problem:
| START1 | START2 | Spin-up behaviour |
|---|---|---|
| 0 | 0 | Automatic, immediate |
| 0 | 1 | Wait for Start Unit SCSI command |
| 1 | 0 | Staggered, delayed depending on loop address |
| 1 | 1 | Reserved |
DEVCTRL options - a disk that has the wrong interface speed can cause serious problems if it is inserted into an enclosure. That problem is avoided by providing three input pins to the disk that define the interface speed at which it will operate:
| DEVCTRLx value | Interface speed |
|---|---|
| 0-4 | Reserved |
| 5 | 4 GB/s |
| 6 | 2 GB/s |
| 7 | 1 GB/s |
In computer architecture, a bus is a communication system that transfers data between components inside a computer, or between computers. This expression covers all related hardware components and software, including communication protocols.
In telecommunications, RS-232 or Recommended Standard 232 is a standard originally introduced in 1960 for serial communication transmission of data. It formally defines signals connecting between a DTE such as a computer terminal or PC, and a DCE, such as a modem. The standard defines the electrical characteristics and timing of signals, the meaning of signals, and the physical size and pinout of connectors. The current version of the standard is TIA-232-F Interface Between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997.
Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices, best known for its use with storage devices such as hard disk drives. SCSI was introduced in the 1980s and has seen widespread use on servers and high-end workstations, with new SCSI standards being published as recently as SAS-4 in 2017.
A serial port is a serial communication interface through which information transfers in or out sequentially one bit at a time. This is in contrast to a parallel port, which communicates multiple bits simultaneously in parallel. Throughout most of the history of personal computers, data has been transferred through serial ports to devices such as modems, terminals, various peripherals, and directly between computers.
PCI Express, officially abbreviated as PCIe or PCI-e, is a high-speed serial computer expansion bus standard, designed to replace the older PCI, PCI-X and AGP bus standards. It is the common motherboard interface for personal computers' graphics cards, capture cards, sound cards, hard disk drive host adapters, SSDs, Wi-Fi, and Ethernet hardware connections. PCIe has numerous improvements over the older standards, including higher maximum system bus throughput, lower I/O pin count and smaller physical footprint, better performance scaling for bus devices, a more detailed error detection and reporting mechanism, and native hot-swap functionality. More recent revisions of the PCIe standard provide hardware support for I/O virtualization.
HIPPI, short for High Performance Parallel Interface, is a computer bus for the attachment of high speed storage devices to supercomputers, in a point-to-point link. It was popular in the late 1980s and into the mid-to-late 1990s, but has since been replaced by ever-faster standard interfaces like Fibre Channel and 10 Gigabit Ethernet.
SATA is a computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives. Serial ATA succeeded the earlier Parallel ATA (PATA) standard to become the predominant interface for storage devices.
In telecommunication and data transmission, serial communication is the process of sending data one bit at a time, sequentially, over a communication channel or computer bus. This is in contrast to parallel communication, where several bits are sent as a whole, on a link with several parallel channels.
DMX512 is a standard for digital communication networks that are commonly used to control lighting and effects. It was originally intended as a standardized method for controlling stage lighting dimmers, which, prior to DMX512, had employed various incompatible proprietary protocols. It quickly became the primary method for linking controllers to dimmers and special effects devices such as fog machines and intelligent lights.
The Attachment Unit Interface (AUI) is a physical and logical interface defined in the IEEE 802.3 standard for 10BASE5 Ethernet and the earlier DIX standard. The physical interface consists of a 15-pin D-subminiature connector that links an Ethernet node's physical signaling to the Medium Attachment Unit (MAU), sometimes referred to as a transceiver. An AUI cable can extend up to 50 metres, though often the MAU and data terminal equipment's (DTE) medium access controller (MAC) are directly connected, bypassing the need for a cable. In Ethernet implementations where the DTE and MAU are combined, the AUI is typically omitted.
Serial Storage Architecture (SSA) was a serial transport protocol used to attach disk drives to server computers. It was developed by IBM employee Ian Judd in 1990 to provide data redundancy for critical applications. SSA was deployed in server RAID environments, where it was capable of providing for up to 80 MB/s of data throughput, with sustained data rates as high as 60 MB/s in non-RAID mode and 35 MB/s in RAID mode.
The Video Graphics Array (VGA) connector was a standard connector used for computer video output. Originating with the 1987 IBM PS/2 and its VGA graphics system, the 15-pin connector went on to become ubiquitous on PCs, as well as many monitors, projectors and HD television sets.
RS-485, also known as TIA-485(-A) or EIA-485, is a standard, originally introduced in 1983, defining the electrical characteristics of drivers and receivers for use in serial communications systems. Electrical signaling is balanced, and multipoint systems are supported. The standard is jointly published by the Telecommunications Industry Association and Electronic Industries Alliance (TIA/EIA). Digital communications networks implementing the standard can be used effectively over long distances and in electrically noisy environments. Multiple receivers may be connected to such a network in a linear, multidrop bus. These characteristics make RS-485 useful in industrial control systems and similar applications.
A breakout box is a piece of electrical test equipment used to support integration testing, expedite maintenance, and streamline the troubleshooting process at the system, subsystem, and component-level by simplifying the access to test signals. Breakout boxes span a wide spectrum of functionality. Some serve to break out every signal connection coming into a unit, while others breakout only specific signals commonly monitored for either testing or troubleshooting purposes. Some have electrical connectors, and others have optical fiber connectors.
The PS/2 port is a 6-pin mini-DIN connector used for connecting keyboards and mice to a PC compatible computer system. Its name comes from the IBM Personal System/2 series of personal computers, with which it was introduced in 1987. The PS/2 mouse connector generally replaced the older DE-9 RS-232 "serial mouse" connector, while the PS/2 keyboard connector replaced the larger 5-pin/180° DIN connector used in the IBM PC/AT design. The PS/2 keyboard port is electrically and logically identical to the IBM AT keyboard port, differing only in the type of electrical connector used. The PS/2 platform introduced a second port with the same design as the keyboard port for use to connect a mouse; thus the PS/2-style keyboard and mouse interfaces are electrically similar and employ the same communication protocol. However, unlike the otherwise similar Apple Desktop Bus connector used by Apple, a given system's keyboard and mouse port may not be interchangeable since the two devices use different sets of commands and the device drivers generally are hard-coded to communicate with each device at the address of the port that is conventionally assigned to that device.
IEEE Standard 1355-1995, IEC 14575, or ISO 14575 is a data communications standard for Heterogeneous Interconnect (HIC).
Asynchronous Serial Interface, or ASI, is a method of carrying an MPEG Transport Stream (MPEG-TS) over 75-ohm copper coaxial cable or optical fiber. It is popular in the television industry as a means of transporting broadcast programs from the studio to the final transmission equipment before it reaches viewers sitting at home.
A SCSI connector is used to connect computer parts that communicate with each other via the SCSI standard. Generally, two connectors, designated male and female, plug together to form a connection which allows two components, such as a computer and a disk drive, to communicate with each other. SCSI connectors can be electrical connectors or optical connectors. There have been a large variety of SCSI connectors in use at one time or another in the computer industry. Twenty-five years of evolution and three major revisions of the standards resulted in requirements for Parallel SCSI connectors that could handle an 8, 16 or 32 bit wide bus running at 5, 10 or 20 megatransfer/s, with conventional or differential signaling. Serial SCSI added another three transport types, each with one or more connector types. Manufacturers have frequently chosen connectors based on factors of size, cost, or convenience at the expense of compatibility.
Parallel SCSI is the earliest of the interface implementations in the SCSI family. SPI is a parallel bus; there is one set of electrical connections stretching from one end of the SCSI bus to the other. A SCSI device attaches to the bus but does not interrupt it. Both ends of the bus must be terminated.
Hard disk drives are accessed over one of a number of bus types, including parallel ATA, Serial ATA (SATA), SCSI, Serial Attached SCSI (SAS), and Fibre Channel. Bridge circuitry is sometimes used to connect hard disk drives to buses with which they cannot communicate natively, such as IEEE 1394, USB, SCSI, NVMe and Thunderbolt.