USB Device Controller
1574
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Universal Serial Bus (USB)
Table 29-40. Device Status Register (DEVSTAT) Field Descriptions (continued)
Bit
Field
Value
Description
5
USB_RESET
USB reset signaling is active. The USB_RESET bit returns 1 when the USB host resets the
USB bus. A valid USB reset resets the endpoint FIFOS, the other control register bits, except
for SYSCON1.CFG_LOCK and the associated configuration registers (0x20 to 0x3F),
IRQ_EN.DS_CHG_IE and IRQ_SRC.DS_CHG, and forces the device to the default state for
DEVSTAT (this register). This bit is cleared at the end of reset. This bit, as well as other
DEVSTAT bits, is double-buffered. If a pending interrupt has not been handled when a USB
reset occurs and is handled only when USB reset is finished, the USB device controller does
not see the USB_RESET bit going high and then low.
0
Device is not being reset by USB host.
1
Device is being reset by USB host.
The value after the USB device controller hardware reset is low, and during USB reset is high
(low after USB reset).
4
SUS
Suspended state bit: the device in suspended state is, at a minimum, attached to the USB,
powered, has been reset by the USB host, and has not seen bus activity for 5 ms. It can also
have a unique address and be configured for use. Because the device is suspended, however,
the host cannot use the device function. This bit returns 1 when the USB device is in a
suspended state.
0
Not suspended
1
Suspended
Value after system reset or USB reset is low.
3
CFG
Configured state bit: the device is attached to the USB, powered, has been reset, has a unique
address, and is configured. The host can use the function provided by the device. This bit
returns 1 when the USB device has been configured after a set SYSCON2.DEV_CFG = 1. This
bit remains set to 1 until the device becomes deconfigured. This bit is cleared when the core
receives a valid SET_CONFIGURATION request and the USB device controller sets the
SYSCON2.CLR_CFG bit. During the time this bit is not set to 1, transactions that are not for
control EP0 are ignored. A GET_ENDPOINT_STATUS to a non-control endpoint is stalled.
0
Not configured
1
Configured
Value after system reset or USB reset is low.
2
ADD
Addressed state bit: the device is attached to the USB, powered, has been reset, and a unique
device address has been assigned. This bit (ADD) returns 1 after an ET_ADDRESS standard
request. This bit remains set to 1 until the device becomes de-addressed.
0
Not addressed
1
Addressed
Value after system reset or USB reset is low.
1
DEF
The default state bit returns 1 when the USB device is attached to the USB and powered, and
has been reset. This bit remains set to 1 until the device becomes de-powered. The device
moves into default state as soon as the USB reset is effective.
0
Not in default
1
Default
The value after CPU is low, and after USB reset is high.
0
ATT
The attached state bit returns 1 when the device is attached to the USB and is powered. This
bit remains set to 1 until the device powers down.
0
Not attached
1
Attached
The value after USB device controller hardware reset is low (unattached) or high (attached),
and after USB reset is high.