21.4 USB0 Control Registers
21.4.1 USB0XCN: USB0 Transceiver Control
Bit
7
6
5
4
3
2
1
0
Name
PREN
PHYEN
SPEED
PHYTST
DFREC
Dp
Dn
Access
RW
RW
RW
RW
R
R
R
Reset
0
0
0
0x0
0
0
0
SFR Page = 0x20; SFR Address: 0xB3
Bit
Name
Reset
Access Description
7
PREN
0
RW
Internal Pull-up Resistor Enable.
The location of the pull-up resistor (D+ or D-) is determined by the SPEED bit.
Value
Name
Description
0
PULL_UP_DISABLED
Internal pull-up resistor disabled (device effectively detached from USB
network).
1
PULL_UP_ENABLED
Internal pull-up resistor enabled when VBUS is present (device attach-
ed to the USB network).
6
PHYEN
0
RW
Physical Layer Enable.
Value
Name
Description
0
DISABLED
Disable the USB0 physical layer transceiver (suspend).
1
ENABLED
Enable the USB0 physical layer transceiver (normal).
5
SPEED
0
RW
USB0 Speed Select.
This bit selects the USB0 speed.
Value
Name
Description
0
LOW_SPEED
USB0 operates as a Low Speed device. If enabled, the internal pull-up
resistor appears on the D- line.
1
FULL_SPEED
USB0 operates as a Full Speed device. If enabled, the internal pull-up
resistor appears on the D+ line.
4:3
PHYTST
0x0
RW
Physical Layer Test.
Value
Name
Description
0x0
MODE0
Mode 0: Normal (non-test mode) (D+ = X, D- = X).
0x1
MODE1
Mode 1: Differential 1 forced (D+ = 1, D- = 0).
0x2
MODE2
Mode 2: Differential 0 forced (D+ = 0, D- = 1).
0x3
MODE3
Mode 3: Single-Ended 0 forced (D+ = 0, D- = 0).
2
DFREC
0
R
Differential Receiver.
The state of this bit indicates the current differential value present on the D+ and D- lines when PHYEN = 1.
Value
Name
Description
0
DIFFERENTIAL_ZERO Differential 0 signalling on the bus.
EFM8UB3 Reference Manual
Universal Serial Bus (USB0)
silabs.com
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