USB Host Controller Registers
14-23
Universal Serial Bus Host
The HC frame remaining register reports the number of full speed bit times
remaining in the current frame.
Table 14–16. HC Frame Remaining Register (HcFmRemaining)
Bit
Name
Description
Type
Reset
Value
31
FRT
Frame remaining toggle
This bit is loaded with the frame interval toggle bit every time
the USB host controller loads the frame interval field into the
frame remaining field.
R
0
30–14
Reserved
Reserved
13–0
FR
Frame remaining
The number of full speed bit times remaining in the current
frame. This field is automatically reloaded with the frame
interval field value at the beginning of every frame.
R
0
The HC frame number register reports the current USB frame number.
Table 14–17. HC Frame Number Register (HcFmNumber)
Bit
Name
Description
Type
Reset
Value
31–16
Reserved
Reserved
15–0
FN
Frame number
This field reports the current USB frame number. It is
incremented when the frame remaining field is reloaded with
the frame interval field value. Frame number automatically
rolls over from 0xFFFF to 0x0000.
After frame number is incremented, its new value is written to
the HCCA and the USB host controller sets the SOF interrupt
status bit and begins processing the ED lists.
R
0