USB Device Controller
1571
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Universal Serial Bus (USB)
Table 29-37. System Configuration Register 1 (SYSCON1) Field Descriptions (continued)
Bit
Field
Value
Description
2
SELF_PWR
The self-powered bit indicates to the USB host whether the device is bus-powered or self-powered.
This information is needed for an autodecoded request. The USB device controller must update this
bit after a SET_CONFIGURATION according to the self-powered bit D6 given in the configuration
descriptor (see
USB 1.1 Specification
).
0
Bus powered
1
Self-powered
The value after USB device controller hardware reset is low; after USB reset, it is unchanged.
1
SOFF_DIS
When the shutoff disable bit is set, it disables the power shutoff circuitry.
0
Power shutoff circuitry is enabled.
1
Power shutoff circuitry is disabled.
The value after USB device controller hardware reset is low; after USB reset, it is unchanged.
0
PULLUP_EN
The external pullup enable bit allows the device to disconnect itself from the USB bus, forcing the
host to reset and reconfigure the device
.
This bit can be used to prevent USB traffic when the
device is not ready.
0
Pull-up is disabled. USB host cannot detect the device. In this mode, the 48-MHz USB clock is
forced off.
1
Pull-up is enabled.
The value after USB device controller hardware reset is low; after USB reset, it is high; and after
detach, it is unchanged.
Table 29-38. Little-Endian and Big-Endian Formats
Little-Endian Format (16 bits):
Big-Endian Format (16 bits):
15
8
7
0
15
8
7
0
Byte 1
Byte 0
Byte 0
Byte 1