Host controller capability parameters
| ADC | 64-bit Addressing Capability. If zero, no 64-bit addressing capability is supported. |
| PFL | Programmable Frame List Flag. If set to one, then the system software can specify and use a smaller frame list and configure the host controller via the USBCMD register Frame List Size field. The frame list must always be aligned on a 4K-boundary. This requirement ensures that the frame list is always physically contiguous. |
| ASP | Asynchronous Schedule Park Capability. If this bit is set to a one, then the host controller supports the park feature for high-speed queue heads in the Asynchronous Schedule.The feature can be disabled or enabled and set to a specific level by using the Asynchronous Schedule Park Mode Enable and Asynchronous Schedule Park Mode Count fields in the USBCMD register. |
| IST | Isochronous Scheduling Threshold. This field indicates, relative to the current position of the executing host controller, where software can reliably update the isochronous schedule. |
| EECP | EHCI Extended Capabilities Pointer. This optional field indicates the existence of a capabilities list. |
| RESERVED | These bits are reserved and should be set to zero. |