Universal Serial Bus OHCI Host Controller User's Guide

3.15 HC Frame Remaining Register (HCFMREMAINING)
3.16 HC Frame Number Register (HCFMNUMBER)
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The HC frame remaining register (HCFMREMAINING) reports the number of full-speed bit times
remaining in the current frame. HCFMREMAINING is shown in Figure 16 and described in Table 16 .
Figure 16. HC Frame Remaining Register (HCFMREMAINING)
31 30 16
FRT Reserved
R-0 R-0
15 14 13 0
Reserved FR
R-0 R-0
LEGEND: R = Read only; - n = value after reset
Table 16. HC Frame Remaining Register (HCFMREMAINING) Field Descriptions
Bit Field Value Description
31 FRT 0-1 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.
30-14 Reserved 0 Reserved
13-0 FR 0-3FFFh Frame remaining. The number of full-speed bit times remaining in the current frame. This field is
automatically reloaded with the frame interval (FI) value in the HC frame interval register
(HCFMINTERVAL) at the beginning of every frame.
The HC frame number register (HCFMNUMBER) reports the current USB frame number. HCFMNUMBER
is shown in Figure 17 and described in Table 17 .
Figure 17. HC Frame Number Register (HCFMNUMBER)
31 16
Reserved
R-0
15 0
FN
R-0
LEGEND: R = Read only; - n = value after reset
Table 17. HC Frame Number Register (HCFMNUMBER) Field Descriptions
Bit Field Value Description
31-16 Reserved 0 Reserved
15-0 FN 0-FFFFh Frame number. This field reports the current USB frame number. It is incremented when the frame
remaining field is reloaded with the frame interval (FI) value in the HC frame interval register
(HCFMINTERVAL). Frame number automatically rolls over from FFFFh to 0. 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.
Universal Serial Bus OHCI Host Controller24 SPRUFM8 – September 2008
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