A multi-gigabit transceiver (MGT) is a

SerDes {{Use American English, date = March 2019 A Serializer/Deserializer (SerDes) is a pair of functional blocks commonly used in high speed communications to compensate for limited input/output. These blocks convert data between serial data and paral ...

capable of operating at serial bit rates above 1 Gigabit/second. MGTs are used increasingly for data communications because they can run over longer distances, use fewer wires, and thus have lower costs than parallel interfaces with equivalent data throughput.

Functions

Like other

, the primary function of the MGT is to transmit parallel data as stream of serial bits, and convert the serial bits it receives to parallel data. The most basic performance metric of an MGT is its serial bit rate, or line rate, which is the number of serial bits it can transmit or receive per second. Although there is no strict rule, MGTs can typically run at line rates of 1 Gigabit/second or more. MGTs have become the 'data highways' for data processing systems that demand a high in/out raw data input and output (e.g. video processing applications). They are becoming very common on

FPGA A field-programmable gate array (FPGA) is an integrated circuit designed to be configured by a customer or a designer after manufacturinghence the term ''Field-programmability, field-programmable''. The FPGA configuration is generally specifi ...

- such programmable logic devices being especially well fitted for parallel data processing algorithms. Beyond serialization and de-serialization, MGTs must incorporate a number of additional technologies to allow them to operate at high line rates. Some of these are listed below:

Signal integrity and jitter

Signal integrity Signal integrity or SI is a set of measures of the quality of an electrical signal. In digital electronics, a stream of binary values is represented by a voltage (or current) waveform. However, digital signals are fundamentally analog in nature, ...

is critical for MGTs due to their high line rates. The quality of a given high-speed link is characterized by the bit error ratio (BER) of the connection (the ratio of bits received in error to total bits received), and

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 ...

. BER and jitter are functions of the entire MGT connection, including the MGTs themselves, their serial lines, their reference clocks, their power supplies, and the digital systems that create and consume their parallel data. As a result, MGTs are often measured by how little jitter they transmit (Jitter Transfer/Jitter Generation), and how much jitter they can tolerate before their BER is too high (Jitter Tolerance). These measurements are commonly taken using a BERT, and analyzed using an

eye diagram In telecommunication, an eye pattern, also known as an eye diagram, is an oscilloscope display in which a digital signal from a receiver is repetitively sampled and applied to the vertical input, while the data rate is used to trigger the horiz ...

Other considerations

Some other metrics for MGTs include: * Maximum run length before loss of CDR lock * Power consumption * Flexibility (e.g. multiple line rates, multiple encodings) * Differential swing (max differential signal the MGT can drive) * Receiver sensitivity (min differential signal the MGT can detect) *

Common-mode rejection ratio In electronics, the common mode rejection ratio (CMRR) of a differential amplifier (or other device) is a metric used to quantify the ability of the device to reject common-mode signals, i.e. those that appear simultaneously and in-phase on both ...

Protocols that use MGTs

MGTs are used in the implementation of the following serial protocols: * 2.5GBASE-T and 5GBASE-T *

10 Gigabit Ethernet 10 Gigabit Ethernet (10GE, 10GbE, or 10 GigE) is a group of computer networking technologies for transmitting Ethernet frames at a rate of 10 gigabits per second. It was first defined by the IEEE 802.3ae-2002 standard. Unlike previous Et ...

Aurora An aurora (plural: auroras or aurorae), also commonly known as the polar lights, is a natural light display in Earth's sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic). Auroras display dynamic patterns of bri ...

CEI-6G
* CPRI *

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 c ...

Gigabit Ethernet In computer networking, Gigabit Ethernet (GbE or 1 GigE) is the term applied to transmitting Ethernet frames at a rate of a gigabit per second. The most popular variant, 1000BASE-T, is defined by the IEEE 802.3ab standard. It came into use i ...

GPON G.984, commonly known as GPON (gigabit-capable passive optical network), is a standard for passive optical networks (PON) published by the ITU-T. It is commonly used to implement the outermost link to the customer (last kilometre or last mile) of ...

* HD-SDI * CoaXPress *

Infiniband InfiniBand (IB) is a computer networking communications standard used in high-performance computing that features very high throughput and very low latency. It is used for data interconnect both among and within computers. InfiniBand is also us ...

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* OBSAI *

PCI Express PCI Express (Peripheral Component Interconnect 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 m ...

* SAS (Serial Attached SCSI) *

Serial ATA SATA (Serial AT Attachment) 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) standar ...

SerialLite
*

Serial RapidIO The RapidIO architecture is a high-performance packet-switched electrical connection technology. RapidIO supports messaging, read/write and cache coherency semantics. Based on industry-standard electrical specifications such as those for Eth ...

SFI-5
*

SONET/SDH Synchronous optical networking (SONET) and synchronous digital hierarchy (SDH) are standardized protocols that transfer multiple digital bit streams synchronously over optical fiber using lasers or highly coherent light from light-emitting ...

XAUI 10 Gigabit Attachment Unit Interface (XAUI ) is a standard for extending the XGMII (10 Gigabit Media Independent Interface) between the MAC and PHY layer of 10 Gigabit Ethernet (10GbE) defined in Clause 47 of the IEEE 802.3 standard. The name i ...

References

High Speed Digital Design, Johnson & Graham

Signal Integrity Simplified, Bogatin

Handbook of Digital Techniques for High Speed Design, Granberg
*

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 ...

FPGA blog : using multi-gigabit transceivers to test and debug FPGA

External links

Xilinx Aurora (Xilinx Inc.)
{{Webarchive, url=https://web.archive.org/web/20051018025434/http://www.xilinx.com/aurora/ , date=2005-10-18
Serial Multi-Protocol Transmission with the LatticeSC FPGA (Lattice Semiconductor)

Virtex-5 RocketIO GTP Transceiver User Guide (Xilinx Inc.)

Stratix II GX Transceiver User Guide (Altera Inc.)
Telecommunications equipment