USB-Disk Module
AP-UMxxxxXXXXG-XXXX
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© 2008 Apacer Technology, Inc. Rev. 1.0
Apacer’s USB-Disk Module (UDM) is a high perform ance, embedded solid state drive (SSD) designed to
replace a c onventional IDE hard disk drive. UDM SSD can be plugged into a standard Em bedded USB
connector commonly found in desktops, portable PC systems and industrial PC systems. This product is
well suited for embedded flash storage applications offering new and expa nded functionality as well as
more cost-effective designs, better performance and increased reliabilit y.
1.1 Performance-optimized Controller
The heart of an UDM is t he USB controller, which translates standard USB signals into the data and
controls of the flash media. This proprietary USB controller is specifically designed to attain high data
throughput from host to flash.
1.1.1 Power Management Unit (PMU)
The po wer management unit (PMU) controls the power consumption of the UDM. I t can dramatically
extend product battery life by leaving the idle part of the circuitry into sleep mode. T he PMU has zero
wake-up latency.
1.1.2 SRAM Buffer
The SRAM buffer is a key contributor to the USB con troller performance. It optimizes data writes to the
flash.
1.1.3 Error Correction Code (ECC)
The UDM uses BCH Error Detection Code (EDC) and Error Correction Code (ECC) algorithms which
correct up to four ran dom single-bit errors for each 51 2-byte block of data. High perf ormance is achieved
through hardware-based error detection and correction.
1.1.4 Wear-Leveling
Flash memory can be erased a limited number of times, This number is called the erase cycle limit, or
write endurance limit, The erase cycle limit applies to each individual erase b lock in the flash device.
In a typical application, and especially if a f ile system is used, specific pages are constantly updated (e.g.,
the page that contains the FAT, registry, etc.). Without any spec ial handling, these pages would wear out
more rapidly than other pages, reducing the lifetime of the entire flash.
To overcome this inherent deficiency, Apacer’s USB-Disk Module (UDM) uses wear-leveling algorithm.
This wear-leveling algorithm ensures that consecutive writes of a specific sector are not written physically
to the same page in the flash. This spreads flash media usage evenl y across all pages, thereby
maximizing flash lifetime.
The wear-leveling mechanism provides more than 100,000 write/erase cycles for reliable data storage
over an extended period.
1.1.5 Write Protection Mode (Optional)
When the device is configured to the W rite-Protection mode, it enhances the data security and protection.
This feature prevents the stored data from inadvertent system writes or er ases, and viruses.