The Fibre Channel electrical interface is one of two related
Fibre Channel
Fibre Channel (FC) is a high-speed data transfer protocol providing in-order, lossless delivery of raw block data. Fibre Channel is primarily used to connect computer data storage to servers in storage area networks (SAN) in commercial data cen ...
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 signal characteristics
Fibre channel electrical signals are sent over a
duplex differential interface. This usually consists of twisted-pair cables with a nominal
impedance of 75
ohm
Ohm (symbol Ω) is a unit of electrical resistance named after Georg Ohm.
Ohm or OHM may also refer to:
People
* Georg Ohm (1789–1854), German physicist and namesake of the term ''ohm''
* Germán Ohm (born 1936), Mexican boxer
* Jörg Ohm (b ...
s (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
Capacitive coupling (electronics), coupling is the transfer of energy within an electrical network or between distant networks by means of displacement current between circuit(s) node (circuits) , nodes, induced by the electric field. This coupl ...
, 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
gigabit
The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represented a ...
s per second.
The
Bit-Error Rate
In digital transmission, the number of bit errors is the number of received bits of a data stream over a communication channel that have been altered due to noise, interference, distortion or bit synchronization errors.
The bit error rate (BER) i ...
(BER) objective for Fibre Channel systems is 1 in 10
12 (1 bit in 1,000,000,000,000 bits). At 2
Gbit
The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represented ...
/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
In electronics and telecommunications, jitter is the deviation from true periodicity of a presumably periodic signal, often in relation to a reference clock signal. In clock recovery applications it is called timing jitter. Jitter is a significa ...
"budgets" are defined for the transmitter and cables.
Fibre Channel connector pinouts
There are various Fibre Channel
connectors in use in the computer industry. Details of their
pinout
In electronics, a pinout (sometimes written "pin-out") is a cross-reference between the contacts, or ''pins'', of an electrical connector or electronic component, and their functions. "Pinout" now supersedes the term "basing diagram" that was the s ...
s 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
''Targets'' is a 1968 American crime thriller film directed by Peter Bogdanovich, produced by Roger Corman, and written by Polly Platt and Bogdanovich, with cinematography by László Kovács.Stephen Jacobs, ''Boris Karloff: More Than a Monster' ...
(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.
9-pin "
DE-9
The D-subminiature or D-sub is a common type of electrical connector. They are named for their characteristic D-shaped metal shield. When they were introduced, D-subs were among the smallest connectors used on computer systems.
Description, n ...
" cable connector
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
Token Ring network
IBM hermaphroditic connector with locking clip. Screen contacts are prominently visible, gold-plated signal contacts less so.
Token Ring is a computer networking technology used to build local area networks. It was introduc ...
, this is an easy way to tell a fibre channel cable from an
RS-232
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'' (''data terminal equipment'') such a ...
cable.
8-pin " HSSDC" cable connector (High Speed Serial Data Connection)
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).
7-pin " HSSDC2" cable connector (High Speed Serial Data Connection)
40-pin "SCA-2" disk connector
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.
Disk options
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:
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:
{, class="wikitable"
, DEVCTRLx value, , Interface speed
, -
, 0-4, , Reserved
, -
, 5, , 4
GB/s
, -
, 6, , 2 GB/s
, -
, 7, , 1 GB/s
, -
External links
Fibre Channel Physical Interface specificationPictures of SSA connectors
Fibre Channel