Hi Erik! I don't know what is exactly your project about, but if you need a reference design concerning ATA interfacing take a look at Cypress. Search for reference design CY4611 (this design reference design uses the 56pin version of the FX2 uC). Also Philips has an application note about ISP1581 (USB-to-ATA bridge) an how to interface it to 8051. But, as Michael commented, give us more info.

Regards,
George Pallis