What USB Phy would bolt up to a CAST CUSB core?

The SLS USB 1.1 Device IP may use either the Fairchild USB1T11AM or Micrel MIC2551A-2.5 PHY chips.

The Micrel PHY is a fine choice for the CAST core and we have tested it. Also, Philips PDIUSBP11A and most any other 1.1 PHY will work. There are far fewer issues here than with 2.0 PHY.