While virtually all consumer hard disk drives that are shipped today are designed to work with Serial ATA interconnection, there is growing demand for external HDDs that should support interconnection standards like USB 2.0. While there is a number of single-chip Parallel ATA-to-USB converters, up to today the world did not have a single Serial ATA-to-USB 2.0 chip, announced by UK-based Oxford Semiconductor.

Oxford Semiconductor’s OXU921S is a highly integrated bridge chip that simplifies implementation of external hard disk and optical disk drives for both PC and Mac platforms. The OXU921S features an integral SATA PHY, USB2.0 PHY and ARM7TDMI processor. The USB mass storage device firmware provided with the chip ensures its full compatibility with standard operating system drivers.

The bridge chip’s embedded USB2.0 Link and PHY support full and high-speed modes and offer backwards compatibility with USB1.1. The OXU921S has a 6KB cache for USB data, facilitating a data transmission speed up to 480Mbps, or about 60GB. The integrated SATA core and PHY operate at 1.50GHz, resulting in a disk interface data rate of 150MB/s.

The use of ARM7 processor, with 8KB close coupled RAM, means users are free to create highly differentiated external SATA drive enclosures through custom firmware development. 12 GPIOs further extend the device’s capability. An embedded UART is provided for use in code development and debug and firmware can be programmed through the USB port to help simplify manufacturing and in-field updates.

To optimise the firmware development process, the OXU921S shares a common software base with other Oxford Semiconductor devices and is backed by a full development kit and evaluation board. The OXU921S is available for sub-$5.5 in quantities exceeding 100 thousand units.

The company did not say whether any major HDD maker plans to adopt the Serial ATA-to-USB 2.0 chip.