Cirrus Logic EP93xx User Manual
Page 466
11-26
DS785UM1
Copyright 2007 Cirrus Logic
Universal Serial Bus Host Controller
EP93xx User’s Guide
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FRT:
FrameRemainingToggle. This bit is loaded from the
FrameIntervalToggle field of HcFmInterval whenever
FrameRemaining reaches 0. This bit is used by HCD for
the synchronization between FrameInterval and
FrameRemaining.
HcFmNumber
Address:
0x8002_003C
Default:
0x0000_0000
Definition:
Contains a 16-bit counter used as a timing reference between the host
controller and its driver.
Bit Description:
RSVD:
Reserved. Unknown During Read.
FN:
FrameNumber. This is incremented when
HcFmRemaining is re-loaded. It will be rolled over to 0x0
after 0xFFFF. When entering the USBOPERATIONAL
state, this will be incremented automatically. The content
will be written to HCCA after HC has incremented the
FrameNumber at each frame boundary and sent a SOF
but before HC reads the first ED in that Frame. After
writing to HCCA, HC will set the StartofFrame in
HcInterruptStatus.
HcPeriodicStart
Address:
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RSVD
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
FN
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RSVD
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RSVD
PS