RM0082
HS_USB2.0 host
Doc ID 018672 Rev 1
427/844
[03:02]
FLS
2‘h0
Frame list size.
This 2 bit field specifies the size of the frame list,
according to encoding:
2‘b00 = 102 elements (4096 bytes).
2‘b01 = 512 elements (2048 bytes).
2‘b10 = 256 elements (1024 bytes) - for resource-
constrained environments
2‘b11 = Reserved.
The frame list size set by this field controls which bits
in the FRINDEX register should be used for the frame
list current index.
[01]
HCRESET
1‘h0
Host controller reset.
This control bit is used by software to reset the EHCI
host controller. When software set this bit, the EHCI
host controller resets its internal pipelines, timers,
counters, state machines, etc. to their initial values.
Any transaction currently in progress on USB is
immediately terminated. A USB reset is not driven on
downstream ports. PCI configuration registers are not
affected by this reset. All operational registers,
including port registers and port state machines are
set to their initial values.
Note: Port ownership reverts to the companion OHCI
host controller(s), with the side effects.
This bit is cleared by the EHCI host controller when
the reset process is complete.
Note: Software cannot terminate the reset process
early by writing a 1‘b0 to this field. Software must
reinitialize the EHCI host controller in order to return
to an operational state.
Note: Software setting this bit while HCHalted bit in
USBSTS register is equal to 1‘b0 results in undefined
behavior (because attempting to reset an actively
running EHCI host controller).
[00]
RS
1‘h0
Run / stop.
Setting this bit, the EHCI host controller proceeds
with execution of the schedule, and it continues
execution as long as RS is set.
Clearing this bit, the EHCI host controller completes
the current and any actively pipelined transactions on
the USB and then halts. The HCHalted bit in the
USBSTS register reflects this status.
Note: The EHCI host controller must halt within 16
micro-frames after software clears the RS bit.
Note: In order to avoid undefined results, software
must not set the RS bit until the EHCI host controller
is in the halted state (i.e., HCHalted in the USBSTS
register is set to 1‘b1).
Table 354.
USBCMD register bit assignments (continued)
Bit
Name
Reset value Description