Tech Info - USB and Firewire

USB and FireWire (IEEE 1394a and b) represent the newer generations of external serial interfaces being adopted to reduce PC and connection costs and to improve performance.

USB (1.x and 2.0)

The USB specification defines what are now called standard A and B type connectors. The A type connects to the Host, Hub or Bridge. The Type B connects to the end peripheral. This is shown in diagram 1 below.

The 'On-the-Go (OTG)' specification introduced a Mini-B connector, Micro A and B connectors (in 2007) as well as peer-to-peer operation.

Great to see that the USB folk make their specs freely available unlike the IEEE 1394 folks.

USB 1.x provides low speed (up to 1.5 M Bit/s) at distances of 3m, USB 1.x at high speed (12 M Bit/s) at distances of 5m. Version 2.0 supports speeds to 480 M Bit/s at distances of up to 5m. In all cases a maximum of 5 hubs may be supported.

USB (1.x and 2.0) provide a base current of 100MA and a maximum current of base X 5 = 500MA for powering of peripherals or battery charging applications.

Standard Type A Pin assignment

Pin Name Color Notes 1 VBUS Red Power 2 D- White Data - 3 D+ Green Data + 4 GND Black Ground

Standard Type B Pin assignment

Pin Name Color Notes 1 VBUS Red Power 2 D- White Data - 3 D+ Green Data + 4 GND Black Ground

Mini-USB Type B Pin assignment

Originally defined as part of the 'On-the-Go (OTG)' enhancement, features a single connector mini type B and peer-to-peer operation (the Mini A and AB connectors have been deprecated). The Mini B connector may still be used within the USB standard but not within the OTG standard where it has been replaced with the Micro standard (see below).

Pin Name Color Notes 1 VBUS Red Power 2 D- White Data - 3 D+ Green Data + 4 ID - NC 5 GND Black Ground

Micro-USB Type A/B Pin assignment

Added to the USB and 'On-the-Go (OTG)' enhancement in 2007, features Micro A, Micro B plugs and an A/B receptacle.

Pin Name Color Notes 1 VBUS Red Power 2 D- White Data - 3 D+ Green Data + 4 ID - Micro A - Ground : Type B - NC 5 GND Black Ground Shell Shield - Drain

In addition the Micro-USB connectors mandate the following color coding:

Connector	Color	Notes
Micro A plug	White	-
Micro-B receptacle	Black	-
Micro-B Plug	Black	-
Micro-AB receptacle	Gray	-

USB 3.0

USB 3.0 (November 2008) provides for speeds up to 5.0 G Bit/s - termed SuperSpeed in the specifications. Cable length is not defined in the USB 3.0 standard but lengths of 3m are expected and 5m are available. USB 3.0 uses new Standard and Micro A and B plugs and receptacles using 9 pins to obtain the full SuperSpeed performance (5.0 G Bit/s). A new keying method is used to enable backward connectivity and operation with USB 2.0. Where either a USB 2.0 plug OR receptacle is used the connection is limited to USB 2.0 speeds, whereas when USB 3.0 plugs and receptacles are used USB 3.0 speeds are supported. USB 2.0 Mini-B connectors are not supported within the USB 3.0 specification.

USB 3.0 increases the base current from 100MA (USB 2.0) to 150MA. The maximum load is now 6 x base to 900MA (up from USB 2.0 x 5 = 500MA).

Supported interconnections between USB 2.0 and USB 3.0 are shown in the table below:

Receptacle	Plugs	Notes
USB 2.0 Standard A	USB 2.0 or 3.0 Standard A	-
USB 3.0 Standard A	USB 2.0 or 3.0 Standard A	-
USB 2.0 Standard B	USB 2.0 Standard B	-
USB 3.0 Standard B	USB 2.0 or 3.0 Standard B	-
USB 3.0 Powered B	USB 3.0 Powered B, USB 2.0 or 3.0 Standard B	-
USB 2.0 Micro B	USB 2.0 Micro B	-
USB 3.0 Micro B	USB 2.0 or 3.0 Micro B	-
USB 2.0 Micro AB	USB 2.0 Micro A or Micro B	-
USB 3.0 Micro AB	USB 3.0 Micro A or Micro B, USB 2.0 Micro A or Micro B	-

USB 3.0 Connectors

USB 3.0 uses a 9 pin design (USB 2.0 plugs and receptacles will interconnect as shown in the above table) and defines the following connectors that, when a USB 3.0 plug and receptacle are paired will provide full 5.0 G Bit/s performance:

USB 3.0 Connectors	Housing Color Code	Notes
USB 3.0 Standard A Receptacle	Blue	-
USB 3.0 Standard A Plug	Blue	-
USB 3.0 Standard B Receptacle	-	-
USB 3.0 Standard B Plug	-	-
USB 3.0 Standard B Powered Receptacle	-	Additional 2 pins to Standard B DPWR (Power) and GND
USB 3.0 Standard B Powered Plug	-	Additional 2 pins to Standard B DPWR (Power) and GND
USB 3.0 Micro B Receptacle	-	-
USB 3.0 Micro B Plug	-	-
USB 3.0 Micro A Receptacle	-	Identical to Micro B except keying
USB 3.0 Micro A Plug	-	Identical to Micro B except keying
USB 3.0 Micro AB Receptacle	-	Only receptacle allowed by OTG

USB 3.0 Type A/B Pin assignment

Pin Name Notes 1 VBUS Power 2 D- Data - Differential USB 2.0 3 D+ Data + Differential USB 2.0 4 GND Ground 5 StdA_SSRX- Differential SuperSpeed RX 6 StdA_SSRX+ Differential SuperSpeed RX 7 GND_DRAIN Signal Ground Return 8 StdA_SSTX- Differential SuperSpeed TX 9 StdA_SSTX+ Differential SuperSpeed TX Shell Shield Drain

Notes:

1. Pins 1 - 4 are identical to those of a USB 2.0 Standard A Receptacle allowing interconnection with USB 2.0 devices - though limited to USB 2.0 speeds (480 M Bit/s)

IEEE 1394 (Firewire a.k.a. i.Link)

The IEEE high speed serial connector is known as Firewire and i.Link (Japan). The IEEE 1394a-1995 specification provides up to 400 M bit/sec and uses either a 6 pin connector (PCs/Computers) or a 4 pin connector (camcorders and AV equipment). The latest specification IEEE 1394b provides up to 800 M bit/sec (but is slated for 3.2 G bit/s) and uses a 9 pin connector which may operate in 'biligual mode' (will connect to either a 4 or 6 pin IEEE 1394a connectors but needs a special converter cable) or 'beta mode' (will connect to another IEEE 1394b system).

Firewire uses the Open Host Controller Interface (OHCI)

As always the lack of freely available specifications is just a pain - leading to confusion and plain stupidity. It is a shame that the IEEE 1394 working group could not take a leaf out of the IEEE 802 group which now provides specs at no cost 6 months after their initial publication. Sigh.

Firewire/i.Link 6 Pin Connector Assignment

This connector is usually found on PCs (Apple especially) and disk systems.

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Pin Name Color Notes 1 Power - Power (18V - 25V, 15W) 2 GND - Ground 3 TPB- - Pair B - 4 TPB+ - Pair B + 5 TPA- - Pair A - 6 TPA+ - Pair A +

Firewire/i.Link 4 Pin Connector Assignment

This very compact connector is usually found on camcorders and other digital AV equipment.

Pin Name Color Notes 1 TPB- - Pair B - 2 TPB+ - Pair B + 3 TPA- - Pair A - 4 TPA+ - Pair A +

Firewire/i.Link 9 Pin Connector Assignment

This is the new IEEE 1394b (Firewire 800) connector which allows interconnection to older 1394a systems in 'bilingual mode'(4 or 6 pin - using an appropriate converter cable). In 'beta mode' allows connection to other 1394b systems.

Note: The power specification shown below (12 - 25V) highlights the problems of keeping definitive specifications limited to folks who are prepared to shell out filthy lucre for the privilege of reading the three lines that interest them and the confusion that arises as users legitimately try to reconcile various published specs and product notes. Various device specifications, notes and descriptions contain a variety of specific power values within the range shown below. The majority of chipset specifications use a low figure of 12V, many device descriptions (some based on the same chipsets) maintain the older maximum value of 25V. Since one of the benefits of the 1394b specification is longer cable runs on certain media types we have shown the low value as 12V since this seems to allow for increased voltage drop and consequently makes sense to us. We would be delighted to provide further information and clarification on this topic if anyone cares to update us.

Pin Name Color Notes 1 TPB- - Pair B - 2 TPB+ - Pair B + 3 TPA- - Pair A - 4 TPA+ - Pair A + 5 TPA(R) - Pair A Ground Ref. 6 VG - Power Ground 7 SC - Status Contact (Reserved NC) 8 VP - Power (12-25V DC, 15W) 9 TPB(R) - Pair B Ground Ref

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