OnSpec xSil 259B – Hi-Speed USB Flash Media R/W Controller



OnSpec’s xSil 259B Flash drive Controller further extends the transfer rates of the new and faster NAND flash. The xSil 259B controller supports NAND SLC and NAND MLC flash manufactured by wide range of vendors such as Toshiba, Samsung, Micron, SPECTEK, ST Micro, Hynix, and Infineon. The xSil259B is a complete System-On-Chip (SOC) solution for interfacing flash media based storage to USB 1.1 Full-Speed or USB 2.0 Hi-Speed Bus. The performance is currently benchmarked at 30MB/sec sustained read speed and expect better performance as NAND’s with faster technology are developed. Also includes NOP=1 for recent MLC NAND requirements.

OnSpec offers Reference Designs, Firmware, Drivers, Application and Manufacturing Test Software to make product development easy. OnSpec’s technology provides optimum throughput and superior flash media compatibility. 


  • Supports NAND SLC, NAND MLC media

  • NOP=1 support for MLC NAND

  • 4Byte FEC (Forward Error Correction), better than 4-bit ECC

  • Supports 4 chip selects

  • 48-pin package

  • Full Speed USB (USB1.1) and Hi-Speed USB (USB 2.0) – Bus powered.

  • Compatible with Microsoft Vista (Beta releases), WinXP and Win2K (All versions), Windows Me, Windows 98, Windows 95b (OSR2), Apple OS X and Linux builds with Kernel 2.4 or later Multi-Lun Mass Storage Class Drivers

  • Win2K (up to SP3), Win98/ 98SE, Win 95b(OSR2) and Apple OS8.6 and OS9 Multi-LUN Mass Storage Class Drivers Available

  • Single chip with integrated USB 2.0 PHY

  • Optional Secure partition capability based on SHA-2 algorithm

  • Serial port

  • Two General Purpose Timers

  • Watchdog Timer

  • 16 bit RISC Processor

  • Onboard ROM contains BIOS and Application code.

  • Programmable IOR and IOW widths

  • Optimum hardware controlled transfer for speed and scalability

  • BlockDiagram



Functional Description

The xSil 259B is designed to connect an IDE/ATA device or NAND flash to USB controller. It contains the following:

  •   48-pin 9mm x 9mm LQFP package

  • Single chip with integrated USB 2.0 PHY

  • Serial EEPROM port

  • Supports NAND SLC, NAND MLC media

  • Supports Spansion ORNAND

  • NOP=1 support for MLC NAND

  • 4-byte FEC (Forward Error Correction) in hardware (real time)

  • Firmware enhancements can be stored on On-board NAND

  • Serial port

  • Two General Purpose Timers

  • Watchdog Timer

  • 16 bit Processor

  • Internal RAM for supporting enhancements

  • ROM with BIOS and Application code

  • Programmable Read and Write widths

  • Optimum hardware controlled transfer for speed and scalability


  • Up to 4 Chip selects to allow extended addressing

  • FEC Error detection and correction, which can correct up to 4-bytes of error per sector.

  • Firmware enhancements can be stored on On-board NAND when populated.


The xSil 259B is a 48-pin LQFP package.

USB Engine

The xSil 259B meets the Universal Serial Bus (USB) specification V2.0 and V1.1.

Support for NAND SLC / NAND MLC Flash

The Widespread support for popular NAND SLC / NAND MLC flash media is available. The xSil 259B processor comes with a 4-Byte FEC Error correction algorithm that detects and corrects up to 4 Bytes in a 512 byte block. A programmable clock speed is provided to set the clock speed based on the media’s capabilities. The processor can load firmware from the NAND media itself thus obviating the need for an I2C component.

Serial port
Supports 7200 to 115.2K baud. It can be used as a debug port to communicate with V3 debugger and to load the monitor program.
General Purpose Timers
Two general-purpose timers, Timer0 and Timer1 are provided to allow firmware programmers to keep track of timeouts as well as to generate delays.
Watchdog Timer

A Watchdog Timer is provided to enable catastrophic events to interrupt the processor. The Watchdog Timer overflow causes an internal processor reset. The Processor can read the WT bit after exiting reset to determine if the WT bit is set. If it is set, a watchdog timeout occurred. The timeout is selectable to any of the following values: 2 second, 8 seconds, 16 seconds or 32 seconds.

xSil 259B Processor

The xSil 259B Processor has a built-in 16-bit processor along with a BIOS ROM. The processor operates with a specialized instruction set optimized for Mass Storage applications and USB transaction processing. The start up code for the 16-bit processor resides in a masked ROM.

RAM Interface

The xSil 259B chip comes with Internal RAM for data buffering.

Masked ROM

The Masked ROM consists of the xSil 259B-processor start-up code and the functions listed below:

  • Power On Initialization

  • USB packet transaction management

  • USB Power Management (S0..S3 modes)

  • USB Enumeration Management

  • API support for USB transactions, Memory Management and other functions.

  • Built-in Library functions for Flash devices

The BIOS API functions are designed as Software Interrupts, making it easy for enhancements. Any Interrupt can be enhanced / modified by inserting the user defined function in the interrupt placeholder. When this interrupt is called by the BIOS, the user defined function is called first to enhance the behavior before passing it on to the standard BIOS function’s call or return without passing it on.

Programmable Read and Write cycles

The external cycles to flash using the D[15:0] bus are software configurable.

Ordering Information

Part Number



xSil 259B-G

USB to Flash controller 48 LQFP


(RoHS Compliant)


Technical and Design-in Information

Contact: sales@siliconapps.com

Design Support (Will be provided by OnSpec upon request)

  • NAND Compatibility Testing (Software Release Notes)

  • Read/Write Performance Testing (Software Release Notes)

  • USB IF Certification Lab Report Summary

  • IBIS Models (Available on request)

  • Qualification Report

  • BIOS Boot Over USB Compatibility Testing Report

Available from OnSpec under Software License Agreement (SLA):

  • Click Wrap SLA Agreement for Object Code on OnSpec Website

  • Manufacturing Utilities

  • Software Release Notes (Important for Attribute Bit Settings and Descriptions)

  • Software Test Report (Matrix of OS and PC Chipset Testing)

  • Windows 98 and Windows 2000 Multi-LUN Drivers

  • Email Notification of New Firmware Object Code Downloadable Over the OnSpec Secure Website


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