Universal Host Controller Interface (UHCI) was created by Intel as an implementation of the USB 1.0 host controller interface. Along with OHCI, it makes up the USB 1.0 standard.
Technical Details
The UHCI specification defines a set of I/O mapped registers that allow communication between the controller and the operating system. The base address for these registers can be found by searching the PCI controller for a specific VendorID/DeviceID combination, or for a specific ClassID/SubclassID/Interface combination. All UHCI PCI controllers will have a Class ID of 0x0C, a Subclass ID of 0x03, and an Interface value of 0x00. The PCI Configuration space for this device will contain the I/O port address information in BAR4. This may be different from other standards such as OHCI or EHCI.
I/O Registers
Offset (Hex)
|
Name
|
Description
|
00 |
USBCMD |
Usb Command
|
02 |
USBSTS |
Usb Status
|
04 |
USBINTR |
Usb Interrupt Enable
|
06 |
FRNUM |
Frame Number
|
08 |
FRBASEADD |
Frame List Base Address
|
0C |
SOFMOD |
Start Of Frame Modify
|
10 |
PORTSC1 |
Port 1 Status/Control
|
12 |
PORTSC2 |
Port 2 Status/Control
|
Command Register
Bits
|
Name
|
Description
|
15-8 |
Reserved |
|
7 |
Max Packet |
|
6 |
Configure |
|
5 |
Software Debug |
|
4 |
Global Resume |
|
3 |
Global Suspend |
|
2 |
Global Reset |
|
1 |
Host Controller Reset |
|
0 |
Run |
|
Status Register
Bits
|
Name
|
Description
|
15-6 |
Reserved |
|
5 |
Halted |
|
4 |
Process Error |
|
3 |
System Error |
|
2 |
Resume Detected |
|
1 |
Error Interrupt |
|
0 |
Interrupt |
|
Interrupt Enable Register
Bits
|
Name
|
Description
|
15-4 |
Reserved |
|
3 |
Short Packet |
|
2 |
Complete |
|
1 |
Resume |
|
0 |
Timeout CRC |
|
Port 1/2 Status/Control Registers
Bits
|
Name
|
Description
|
15-13 |
Reserved |
|
12 |
Suspend |
|
11-10 |
Reserved |
|
9 |
Reset |
|
8 |
Low Speed |
|
7 |
Reserved |
(Must be 1)
|
6 |
Resume Detected |
|
5-4 |
Line Status |
|
3 |
Port Enable Changed |
|
2 |
Port Enabled |
|
1 |
Connected Changed |
|
0 |
Connected |
|
Frame List Entry
Bits
|
Name
|
Description
|
31-4 |
First Descriptor Address |
|
3 |
Reserved |
|
2 |
Process Full Queue |
|
1 |
Is Queue |
|
0 |
Is Empty |
|
UHCI Descriptor
Offset (Hex)
|
Name
|
Description
|
Lenght
|
00 |
Next Descriptor |
Same as Frame Entry Above |
4 byte lenght
|
04 |
Status |
See below |
4 byte lenght
|
08 |
Packet Header |
See below |
4 byte lenght
|
12 |
Buffer Address |
32-bit address of data buffer |
4 byte lenght
|
16 |
System Use |
128-bit area reserved for use by the system |
16 byte lenght
|
UHCI Descriptor Status
Bits
|
Name
|
Description
|
31-30 |
Reserved |
|
29 |
Short Packet Detect |
|
28-27 |
Error Counter |
|
26 |
Low Speed |
|
25 |
Is Isochronous |
|
24 |
Interrupt On Complete |
|
23 |
Active |
Set by UHCI Controller
|
22 |
Stalled |
Set by UHCI Controller
|
21 |
Data Buffer Error |
Set by UHCI Controller
|
20 |
Babble Detected |
Set by UHCI Controller
|
19 |
Non-Acknowledged |
Set by UHCI Controller
|
18 |
Timeout CRC |
Set by UHCI Controller
|
17 |
Bit Stuff Error |
Set by UHCI Controller
|
16-11 |
Reserved |
|
10-0 |
Actual Length |
|
Bits
|
Name
|
Description
|
31-21 |
Maximum Length |
(Length - 1)
|
20 |
Reserved |
|
19 |
Data Toggle |
|
18-15 |
Endpoint |
|
14-8 |
Device |
|
7-0 |
Packet Type |
0x69 = IN, 0xE1 = OUT, 0x2D = SETUP
|
See Also