Register Descriptions
1361
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
M3 Universal Serial Bus (USB) Controller
Table 18-63. USB External Power Control Register (USBEPC) Field Descriptions (continued)
Bit
Field
Value
Description
2
EPENDE
EPEN Drive Enable. This bit specifies whether the USB0EPEN signal is driven or undriven (tristate).
When driven, the signal value is specified by the EPEN field. When not driven, the EPEN field is
ignored and the USB0EPEN signal is placed in a high-impedance state.
The USB0EPEN signal is undriven at reset because the sense of the external power supply enable is
unknown. By adding the high-impedance state, system designers can bias the power supply enable to
the disabled state using a large resistor (100 k
Ω
) and later configure and drive the output signal to
enable the power supply.
0
Not Driven. The USB0EPEN signal is high impedance.
1
Driven. The USB0EPEN signal is driven to the logical value specified by the value of the EPEN field.
1-0
EPEN
External Power Supply Enable Configuration. This bit field specifies and controls the logical value driven
on the USB0EPEN signal.
0h
Power Enable Active Low. The USB0EPEN signal is driven Low if the EPENDE bit is set.
1h
Power Enable Active High. The USB0EPEN signal is driven High if the EPENDE bit is set.
2h
Power Enable High if VBUS Low. The USB0EPEN signal is driven High when the A device is not
recognized.
3h
Power Enable High if VBUS High. The USB0EPEN signal is driven High when the A device is
recognized.