HS_USB2.0 host
RM0082
436/844
Doc ID 018672 Rev 1
[11:10]
LS
2’h0
Line status.
This 2 bit field reflects the current logical levels of the D+ (bit
[11]) and D- (bit [10]) signal lines, according to encoding:
2‘b00 SE0 = Not low-speed device, perform EHCI reset.
2‘b01 J-state = Not low-speed device, perform EHCI reset.
2‘b10 K-state = Low-speed device, release ownership of port.
2‘b11 Undefined = Not low-speed device, perform EHCI reset.
These bits are used for detection of low-speed (LS) USB
devices prior to the port reset and enable sequence.
Note: This field is valid only when the port enable bit is 1‘b0
and the current connect status bit is set to 1‘b1.
Note: The value of this field is undefined if port power (PP bit
in this register) is zero.
[09]
Reserved
-
Read: undefined. Write: should be zero.
[08]
PR
1’h0
Port Reset.
This bit states whether the port is in reset, according to
encoding:
1‘b0 = Port is not in reset.
1‘b1 = Port is in reset.
When software writes a 1‘b1 to this bit (from a 1‘b0), the bus
reset sequence as defined in the
Universal Serial Bus
Specification Revision 2.0
is started. Software must keep this
bit at a 1‘b1 long enough to ensure the reset sequence
completes.
Note: When software writes this PR bit to a 1‘b1, it must also
write a 1‘b0 to the port enable bit.
Software writes a 1‘b0 to this bit to terminate the bus reset
sequence.
Note: When software writes a 1‘b0 to this bit there may be a
delay before the bit status changes to a 1‘b0. The bit status will
not read as a 1‘b0 until after the reset has completed.
If the port is in high-speed (HS) mode after reset is complete,
the EHCI host controller will automatically enable this port
(e.g. set the port enable bit to a 1‘b1). A EHCI host controller
must terminate the reset and stabilize the state of the port
within 2 milliseconds of software transitioning this bit from
a1’b1 to a 1‘b0.
Note: The HCHalted bit in the USBSTS register should be a
zero before software attempts to use the PR bit. The EHCI
host controller may hold PR asserted to a one when the
HCHalted bit is a one.
Note: This field is zero if port power (PP bit in this register) is
zero.
Table 362.
PORTSC register bit assignments (continued)
Bit
Name
Reset
value
Description