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) archive copy at the Wayback Machine.
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.

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.

已授權您依據自由軟體基金會發行的無固定段落、封面文字和封底文字GNU自由文件授權條款1.2版或任意後續版本，對本檔進行複製、傳播和／或修改。該協議的副本列在GNU自由文件授權條款中。http://www.gnu.org/copyleft/fdl.htmlGFDLGNU Free Documentation Licensetruetrue

	此檔案採用共享創意 姓名標示-相同方式分享 3.0 未在地化版本授權條款。
	您可以自由： 分享 – 複製、發佈和傳播本作品 重新修改 – 創作演繹作品 惟需遵照下列條件： 姓名標示 – 您必須指名出正確的製作者，和提供授權條款的連結，以及表示是否有對內容上做出變更。您可以用任何合理的方式來行動，但不得以任何方式表明授權條款是對您許可或是由您所使用。 相同方式分享 – 如果您利用本素材進行再混合、轉換或創作，您必須基於如同原先的相同或兼容的條款，來分布您的貢獻成品。
	已新增授權條款標題至此檔案，作為GFDL授權更新的一部份。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