RM0082
HS_USB2.0 host
Doc ID 018672 Rev 1
451/844
Table 377.
HcBulkCurrentED register bit assignments
22.6.38 HcDoneHead
register
The HcDoneHead register contains the physical address of the last completed Transfer
Descriptor that was added to the Done queue. In normal operation, the Host Controller
Driver should not need to read this register as its content is periodically written to the HCCA.
Table 378.
HcDoneHead register bit assignments
22.6.39 Frame
counter
partition
22.6.40 HcFmInterval
register
The HcFmInterval register contains a 14 bit value which indicates the bit time interval in a
Frame, (i.e., between two consecutive SOFs), and a 15 bit value indicating the Full Speed
maximum packet size that the Host Controller may transmit or receive without causing
scheduling overrun. The Host Controller Driver may carry out minor adjustment on the
FrameInterval by writing a new value over the present one at each SOF. This provides the
programmability necessary for the Host Controller to synchronize with an external clocking
resource and to adjust any unknown local clock offset.
Bits
Name
Reset
Read/Write
Description
HCD
HC
[31:04]
BCED
0h
R/W
R/W
BulkCurrentED
This is advanced to the next ED after the HC has served
the present one. HC continues processing the list from
where it left off in the last Frame. When it reaches the end
of the Bulk list, HC checks the ControlListFilled of
HcControl. If set, it copies the content of HcBulkHeadED
to HcBulkCurrentED and clears the bit. If it is not set, it
does nothing. HCD is only allowed to modify this register
when the BulkListEnable of HcControl is cleared. When
set, the HCD only reads the instantaneous value of this
register. This is initially set to zero to indicate the end of
the Bulk list.
[03:00]
Reserved
Bits
Name
Reset
Read/Write
Description
HCD
HC
[31:04]
DH
0h
R
R/W
DoneHead
When a TD is completed, HC writes the content of
HcDoneHead to the NextTD field of the TD. HC then
overwrites the content of HcDoneHead with the address
of this TD. This is set to zero whenever HC writes the
content of this register to HCCA. It also sets the
WritebackDoneHead of HcInterruptStatus.
[03:00]
Reserved