HS_USB2.0 host
RM0082
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Doc ID 018672 Rev 1
22.6.9 USBSTS
register
The USBSTS is a RW register which indicates pending interrupts and various states of the
EHCI host controller. The USBSTS register bit assignments are given in
.
Note:
1
The status resulting from a transaction on the serial bus is not indicated in this register.
2
Software clears a bit in this register by writing a 1‘b1 to it.
Table 355.
USBSTS register bit assignments
Bit
Name
Reset value Description
[31:16]
Reserved
-
Read: undefined. Write: should be zero.
[15]
ASS
1‘h0
Asynchronous schedule status.
The bit reports the current real status of the
asynchronous schedule, according to encoding:
1‘b0 = Disabled.
1‘b1 = Enabled.
The EHCI host controller is not required to
immediately disable or enable the asynchronous
schedule when software transitions the asynchronous
schedule enable bit in the USBCMD register. When
this bit and the asynchronous schedule enable bit are
the same value, the asynchronous schedule is either
enabled or disabled.
[14]
PSS
1‘h0
Periodic schedule status.
The bit reports the current real status of the periodic
schedule, according to encoding:
1‘b0 = Disabled.
1‘b1 = Enabled.
The EHCI host controller is not required to
immediately disable or enable the periodic schedule
when software transitions the periodic schedule
enable bit in the USBCMD register. When this bit and
the periodic schedule enable bit are the same value,
the periodic schedule is either enabled or disabled.
[13]
R
1‘h0
Reclamation.
This is a read-only status bit, which is used to detect
an empty asynchronous schedule.
[12]
HH
1‘h1
HCHalted.
This bit is set by the EHCI host controller after it has
stopped executing as a result of the RS bit (in
USBCMD register being cleared, either by software or
by the EHCI host controller hardware (e.g. internal
error). Besides, this bit is set to 1‘b0 whenever the RS
bit is set to 1‘b1.
[11:06]
Reserved
-
Read: undefined. Write: should be zero.