Universal Serial Bus OHCI Host Controller User's Guide

3.3 HC Command and Status Register (HCCOMMANDSTATUS)
www.ti.com Registers
The HC command and status register (HCCOMMANDSTATUS) shows the current state of the host
controller and accepts commands from the host controller driver. HCCOMMANDSTATUS is shown in
Figure 4 and described in Table 4 .
Figure 4. HC Command and Status Register (HCCOMMANDSTATUS)
31 18 17 16
Reserved SOC
R-0 R-0
15 4 3 2 1 0
Reserved OCR BLF CLF HCR
R-0 R/W-0 R/W-0 R/W-0 R/W-0
LEGEND: R/W = Read/Write; R = Read only; - n = value after reset
Table 4. HC Command and Status Register (HCCOMMANDSTATUS) Field Descriptions
Bit Field Value Description
31-18 Reserved 0 Reserved
17-16 SOC 0-3h Scheduling overrun count. Counts the number of times a scheduling overrun occurs. This count is
incremented even if the host controller driver has not acknowledged any previous pending scheduling
overrun interrupt.
15-4 Reserved 0 Reserved
3 OCR 0-1 Ownership change request. The host controller driver sets this bit to gain ownership of the host
controller. The processor does not support SMI interrupts, so no ownership change interrupt occurs.
2 BLF 0-1 Bulk list filled. The host controller driver must set this bit if it modifies the bulk list to include new TDs. If
the HC current bulk register (HCBULKCURRENTED) is 0, the USB host controller does not begin
processing bulk list EDs unless this bit is set. When the USB host controller sees this bit set and begins
processing the bulk list, it clears this bit to 0.
1 CLF 0-1 Control list filled. The host controller driver must set this bit if it modifies the control list to include new
TDs. If the HC head control register (HCCONTROLHEADED) is 0, the USB host controller does not
begin processing control list EDs unless this bit is set. When the USB host controller sees this bit set
and begins processing the control list, it clears this bit to 0.
0 HCR Host controller reset.
0 No effect.
1 Initiates a software reset of the USB host controller. This transitions the USB host controller to the USB
suspend state. This resets most USB host controller OHCI registers. OHCI register accesses must not
be attempted until a read of this bit returns a 0. A write of 1 to this bit does not reset the root hub and
does not signal USB reset to downstream USB functions.
SPRUFM8 – September 2008 Universal Serial Bus OHCI Host Controller 15
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