Firewire | Technical Characteristics | instrumentic.info

FireWire is the trade name given by Apple to a multiplexed series interface
FireWire is the trade name given by Apple to a multiplexed series interface

FireWire

FireWire is the trade name given by Apple to a multiplexed series interface, also known as the standard IEEE 1394 and also known as the interface i.LINK, trade name used by Sony. It is a computer bus carrying both data and command signals from the various connected devices.


It can be used to connect all kinds of bandwidth-friendly devices that require stable data throughput, especially in hard drives and digital camcorders. It can power a device, as well as connect 63 devices by bus, the connection/disconnection is done while the system is running.
Up to 1,024 buses can be connected via footbridges.
The FireWire was designed at Apple Computer 1986. It became a standard in '95. As a result, other manufacturers, including Sony And Texas Instrument brought to its design.

Technology

FireWire uses a time multiplex : time is cut into 125 microseconds (8,000 cycles per second), with the data cut into packets. In each installment are first transmitted the isochron packages (sound, video) and then the asynchronous packages (data). This system guarantees bandwidth for video streams thus avoiding jerky effects and other quality losses.
Isochron streams are identified by a channel (maximum : 63), and all must have one packet per slice;
once the isochron packages are issued the rest of the cycle is used for asynchronous packages identified not by a channel but by the transmitter ID and the recipient device ID.

Connectors s800 de Apple have 9 pins.
Connectors s800 de Apple have 9 pins.

The formats

The 6-pin format allows device power and the 4-pin format is power-free
Two separate broachings exist in s400 and s800 : the 6-pin format that powers devices and the 4-pin format without power. The four-pin format is that of laptops and mini DV-banded camcorders.
In s800 the connectors have 9 pins.
s400 and s800 are compatible : you can connect a device s800 with a s400 using a 9-pin cable to 6 pins.

The most common cable is twisted copper wire. Its maximum length for all FireWire protocols is 4.5 m. There is also a fibre optic transmission, very expensive but allowing to reach 100 m.

Wiring

1 VCC : 30V
2 Mass
3 TPB- : (twisted pair B) differential signals
4 TPB : (twisted pair B) differential signals
5 TPA- : (twisted pair A) differential signals
6 TPA : (twisted pair A) differential signals

The FireWire provides theoretical speeds that can reach :

100 Mb/s in version 1 IEEE 1394A - S100
200 Mb/s in version 1 IEEE 1394A - S200
400 Mb/s in version 1 IEEE 1394A - S400
800 Mb/s in version 2 IEEE 1394B - S800
1,200 Mb/s in version 2 IEEE 1394B - S1200
1,600 Mb/s in version 2 IEEE 1394B - S1600
3,200 Mb/s in version 2 IEEE 1394B - S3200

Firewire symbol
Firewire symbol

The standard IEEE 1394b can also be called FireWire Gigabit,

FireWire 2
Yes Firewire 800.
The s1600 And s3200 were adopted by theIEEE August 2008.