The internal components of a typical keydrive

This photograph shows both sides of the printed circuit board inside a typical keydrive (Seitec USB-BAR USB 1.1circa 2004), in this case an inexpensive 64 Mbyte USB2.0 device. The plastic clamshell case has been removed.

In practice the keydrive consists of only two significant components. The first is the flash memory part (item 4 in the diagram), a generic device that might as easily be found in a digital camera's memory card. The second (item 2 in the diagram) is a device which implements the USB networking and mass-storage interface, and which knows how to make a chunk of generic flash memory appear like a normal disk drive. The high degree of integration in this latter part makes small, inexpensive keydrives possible.

The parts of the device are as follows:

1. A male type-A USB connector.
2. An Ours Technology Inc. OTi-2168 USB 2.0 mass storage controller. This implements the USB 2.0 host controller, and provides a seamless linear interface to block-oriented serial flash devices, while hiding the complexities of block-orientation, block erasure, and wear balancing. It contains a small RISC microprocessor and a small amount of ROM and RAM. This communicates with the Hynix device over an 8-line unified address/data bus. This version is a 7x7mm 48-pin LQFP (Low Profile Quad Flat Pack) surface-mount device (info).
3. JP1 and JP2: two unpopulated 10-pin connectors, used for testing during the keydrive's manufacture.
4. A Hynix Semiconductor HY27USxx121M series NAND Flash memory device, featuring 4096 independently erasable blocks each providing 16 Kbytes of storage, yielding a total of 64 Mbytes of usable storage. The version used in this keydrive is a 20x12mm 48-pin TSOP1 (Thin Small Outline Package) surface-mount package (datasheet) archive copy at the Wayback Machine.
5. An SKC Shin Chang Electronics 12.000 MHz crystal oscillator (XTAL). The OTi device runs the output of this through a phase-locked loop to produce its main 12 MHz clock signal.
6. A single yellow light-emitting diode (run from a pin on the OTi device) which flashes to indicate activity.
7. A simple two-position switch, used to indicate whether the device should be in "write-protect" mode. It is shown here in the make position, indicating write-protect is off.
8. An unpopulated space for a second TSOP1 memory package. The OTi device is capable of driving up to eight such devices. Having this second space allows the manufacturer to choose (generally on a cost basis) whether to use one or two TSOP flash parts.

Surrounding these main components are a number of tiny surface-mount resistors (many of them serving as pull-ups) and capacitors.

For a closeup of an area of this keydrive, see this image.

Information and licensing

Photographs taken and annotated by John Fader in December 2004 using Adobe Photoshop and Inkscape. This image is (C) Copyright 2004 and (with the exception of its use under the GFDL) all rights are reserved.

Ir dota atļauja kopēt, izplatīt un/vai pārveidot šo dokumentu saskaņā ar GNU brīvās dokumentācijas licences, versijas 1.2 vai jebkuras vēlākas versijas, ko publiskojis Brīvās programmatūras fonds nosacījumiem; bez nemainīgajām sadaļā, priekšējā un aizmugurēja'vāka tekstiem. Licences kopija ir iekļauta sadaļā ar nosaukumu GNU brīvās dokumentācijas licence.http://www.gnu.org/copyleft/fdl.htmlGFDLGNU Free Documentation Licensetruetrue

	Šis fails tiek izplatīts saskaņā ar licences Creative Commons Atsauce-Līdzīgi Noteikumi 3.0 Vispārējiem noteikumiem.
	Jūs varat brīvi: koplietot – kopēt, izplatīt un pārraidīt darbu remiksēt – pielāgot darbu Saskaņā ar šādiem nosacījumiem: atsaucoties – Tev ir jānorāda autors, saite uz licenci un to, vai veiktas kādas izmaiņas. To var darīt jebkādā saprātīgā veidā, bet ne tādā, kas norādītu, ka licencētājs atbalsta tevi vai veidu, kā tu izmanto šo darbu. nemainot licenci – Ja tu miksē, pārveido vai izmanto materiālu, tev savs devums jāpublicē ar to pašu vai saderīgu licenci kā oriģināls.
	This licensing tag was added to this file as part of the GFDL licensing update.http://creativecommons.org/licenses/by-sa/3.0/CC BY-SA 3.0Creative Commons Attribution-Share Alike 3.0truetrue

Originally uploaded by John Fader 17:59, 4 December 2004