OpenHCI

The Host Controller (HC) contains a set of on-chip operational registers which are mapped into a noncacheable portion of the system addressable space. These registers are used by the Host Controller Driver (HCD). According to the function of these registers, they are divided into four partitions, specifically for Control and Status, Memory Pointer, Frame Counter and Root Hub. All of the registers should be read and written as Dwords. 

Reserved bits may be allocated in future releases of this specification. To ensure interoperability, the Host Controller Driver that does not use a reserved field should not assume that the reserved field contains 0. Furthermore, the Host Controller Driver should always preserve the value(s) of the reserved field. When a R/W register is modified, the Host Controller Driver should first read the register, modify the bits desired, then write the register with the reserved bits still containing the read value. Alternatively, the Host Controller Driver can maintain an in-memory copy of previously written values that can be modified and then written to the Host Controller register. When a write to set/clear register is written, bits written to reserved fields should be 0.

Control and Status	HcControl	0x04H	The HcControl register defines the operating modes for the Host Controller.
	HcCommandStatus	0x08H	The HcCommandStatus register is used by the Host Controller to receive commands issued by the Host Controller Driver, as well as reflecting the current status of the Host Controller.
	HcInterruptStatus	0x0CH	This register provides status on various events that cause hardware interrupts.
	HcInterruptEnable	0x10H	Each enable bit in the HcInterruptEnable register corresponds to an associated interrupt bit in the HcInterruptStatus register.The HcInterruptEnable register is used to control which events generate a hardware interrupt.
	HcInterruptDisable	0x14H	Each disable bit in the HcInterruptDisable register corresponds to an associated interrupt bit in the HcInterruptStatus register.
Memory Pointer	HcHCCA	0x18H	The HcHCCA register contains the physical address of the Host Controller Communication Area.
	HcPeriodCurrentED	0x1CH	The HcPeriodCurrentED register contains the physical address of the current Isochronous or Interrupt Endpoint Descriptor.
	HcControlHeadED	0x20H	The HcControlHeadED register contains the physical address of the first Endpoint Descriptor of the Control list.
	HcControlCurrentED	0x24H	The HcControlCurrentED register contains the physical address of the current Endpoint Descriptor of the Control list.
	HcBulkHeadED	0x28H	The HcBulkHeadED register contains the physical address of the first Endpoint Descriptor of the Bulk list.
	HcBulkCurrentED	0x2CH	The HcBulkCurrentED register contains the physical address of the current endpoint of the Bulk list.
	HcDoneHead	0x30H	The HcDoneHead register contains the physical address of the last completed Transfer Descriptor that was added to the Done queue.
Frame Counter	HcFmInterval	0x34H	The HcFmInterval register contains a 14-bit value which indicates the bit time interval in a Frame, (i.e., between two consecutive SOFs), and a 15-bit value indicating the Full Speed maximum packet size that the Host Controller may transmit or receive without causing scheduling overrun.
	HcFmRemaining	0x38H	The HcFmRemaining register is a 14-bit down counter showing the bit time remaining in the current Frame.
	HcFmNumber	0x3CH	The HcFmNumber register is a 16-bit counter. It provides a timing reference among events happening in the Host Controller and the Host Controller Driver.
	HcPeriodicStart	0x40H	The HcPeriodicStart register has a 14-bit programmable value which determines when is the earliest time HC should start processing the periodic list.
	HcLSThreshold	0x44H	The HcLSThreshold register contains an 11-bit value used by the Host Controller to determine whether to commit to the transfer of a maximum of 8-byte LS packet before EOF.
Root Hub	HcRhDescriptorA	0x48H	The HcRhDescriptorA register is the first register of two describing the characteristics of the Root Hub.
	HcRhDescriptorB	0x4CH	The HcRhDescriptorB register is the second register of two describing the characteristics of the Root Hub.
	HcRhStatus	0x50H	The HcRhStatus register is divided into two parts. The lower word of a Dword represents the Hub Status field and the upper word represents the Hub Status Change field.
	HcRhPortStatus[1]	0x54H	The HcRhPortStatus[1:NDP] register is used to control and report port events on a per-port basis.
	…
	HcRhPortStatus[NDP]	54+4*NDP