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SCPS216A – JULY 2009 – REVISED FEBRAURY 2010
8.31 Link Control Register
The link control set/clear register provides the control flags that enable and configure the link core protocol
portions of the controller. It contains controls for the receiver and cycle timer. See
for a
complete description of the register contents.
OHCI register offset:
Register type:
Default value:
BIT NUMBER
RESET STATE
BIT NUMBER
RESET STATE
31
0
15
0
30
0
14
0
29
0
13
0
28
0
12
0
27
0
11
0
E0h set register
E4h clear register
Read/Set/Clear/Update, Read/Set/Clear, Read only
00X0 0X00h
26
0
10
X
25
0
9
X
24
0
8
0
23
0
7
0
22
X
6
0
21
X
5
0
20
X
4
0
19
0
3
0
18
0
2
0
17
0
1
0
16
0
0
0
Table 8-23. Link Control Register Description
BIT
31-23
22
FIELD NAME
RSVD
cycleSource
TYPE
R
RSC
DESCRIPTION
Reserved. Bits 31-23 return 0 0000 0000b when read.
When bit 22 is set to 1b, the cycle timer uses an external source (CYCLEIN) to determine when to
roll over the cycle timer. When this bit is cleared, the cycle timer rolls over when the timer reaches
3072 cycles of the 24.576-MHz clock (125 s).
When bit 21 is set to 1b and the controller is root, it generates a cycle start packet every time the
cycle timer rolls over, based on the setting of bit 22 (cycleSource). When the controller is not root,
regardless of the setting of bit 21, the controller accepts received cycle start packets to maintain
synchronization with the node that is sending them. Bit 21 is automatically cleared when bit 25
(cycleTooLong) in the interrupt event register at OHCI offset 80h/84h (see
is set to
1b. Bit 21 cannot be set to 1b until bit 25 (cycleTooLong) is cleared.
When bit 20 is set to 1b, the cycle timer offset counts cycles of the 24.576-MHz clock and rolls
over at the appropriate time, based on the settings of the previous bits. When this bit is cleared,
the cycle timer offset does not count.
Reserved. Bits 19-11 return 0 0000 0000b when read.
When bit 10 is set to 1b, the receiver accepts incoming PHY packets into the AR request context
if the AR request context is enabled. This bit does not control receipt of self-ID packets.
When bit 9 is set to 1b, the receiver accepts incoming self-ID packets. Before setting this bit to 1b,
software must ensure that the self-ID buffer pointer register contains a valid address.
Reserved. Bits 8 and 7 return 00b when read.
When bit 6 is set to 1b, bit 6 (tag1SyncFilter) in the isochronous receive context match register
(see
is set to 1b for all isochronous receive contexts. When bit 6 is cleared, bit 6
(tag1SyncFilter) in the isochronous receive context match register has read/write access.
Reserved. Bits 5-0 return 00 0000b when read.
21
cycleMaster
RSCU
20
CycleTimerEnable
RSC
19-11
10
9
8-7
6
(1)
RSVD
RcvPhyPkt
RcvSelfID
RSVD
tag1SyncFilterLock
R
RSC
RSC
R
RS
5-0
(1)
RSVD
R
This bit is reset by PERST or FRST.
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1394 OHCI Memory-Mapped Register Space
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