FireWire800 / IDE bridge maximises data throughput

The OXFW912 from Oxford Semiconductor is the first FireWire800 (IEEE1394b) to IDE (ATA7) bridge chip to maximise transfer rates for both single and dual disk drives, irrespective of data block size. When striping data across two drives, the chip can achieve a transfer rate of more than 88Mbytes/sec and maintains its high transfer efficiency even for small data block sizes in single drive applications.

Used with an IEEE1394b PHY, the highly integrated OXFW912 provides a cost effective two-chip solution for smart-cable or tailgate interfaces used in removable media drives, CF card readers, CD, DVD and hard disk drives. The bridge chip is backwards compatible with IEEE1394-1995 and IEEE1394a PHYs and allows IDE drives to take full advantage of FireWire's plug and play functionality.

Following on the success of Oxford's '911 and '922 bridge chips, the 100-pin TQFP packaged OXFW912 features a range of speed enhancements. Supported by the on-board ARM7TDMI processor, an integral serial bus protocol (SBP-2) controller provides extensive hardware acceleration and support for Fast Start. Further improvements assure peak performance for small data block sizes and high speed writes. An on-board ORB coprocessor accelerates ORB to ATA command translation.

Built-in hardware disk striping and spanning functions use the bridge chip's dual IDE master-slave capability to make the best possible use of the high bandwidth offered by the 800Mbits/s FireWire bus. Compliant with the ATA7 and UDMA6 drive standards, the OXFW912 IDE interface also provides 48-bit LBA support for larger drives.

64kbytes of on-board flash program memory means the OXFW912 does not require an external Flash device and firmware is field upgradeable, using the chip's FireWire port. 8kByte RAM and 10kByte cache memory for 1394 data are included. Four GPIO pins and an asynchronous UART further extend the bridge chip's capabilities and the ARM7 processor offers generous spare MIP capacity for custom software design.

Supporting the SBP-2 protocol, the OXFW912 uses generic SBP-2 drivers available in Windows 98 and later versions and Apple Mac OS8.4 operating systems and above. Oxford Semiconductor is providing firmware updates, programming utilities and an OXFW912 FireWire / IDE bridge evaluation board.