C8051T620/1/6/7 & C8051T320/1/2/3
162
Rev. 1.2
SFR Address = 0xD7
SFR Definition 23.1. USB0XCN: USB0 Transceiver Control
Bit
7
6
5
4
3
2
1
0
Name
PREN
PHYEN
SPEED
PHYTST[1:0]
DFREC
Dp
Dn
Type
R/W
R/W
R/W
R/W
R
R
R
Reset
0
0
0
0
0
0
0
0
Bit
Name
Function
7
PREN
Internal Pull-up Resistor Enable.
The location of the pull-up resistor (D+ or D-) is determined by the SPEED bit.
0: Internal pull-up resistor disabled (device effectively detached from USB network).
1: Internal pull-up resistor enabled when VBUS is present (device attached to the
USB network).
6
PHYEN
Physical Layer Enable.
0: USB0 physical layer Transceiver disabled (suspend).
1: USB0 physical layer Transceiver enabled (normal).
5
SPEED
USB0 Speed Select.
This bit selects the USB0 speed.
0: USB0 operates as a Low Speed device. If enabled, the internal pull-up resistor
appears on the D– line.
1: USB0 operates as a Full Speed device. If enabled, the internal pull-up resistor
appears on the D+ line.
4:3
PHYTST[1:0]
Physical Layer Test Bits.
00: Mode 0: Normal (non-test mode) (D+ = X, D- = X)
01: Mode 1: Differential 1 Forced (D+ = 1, D- = 0)
10: Mode 2: Differential 0 Forced (D+ = 0, D- = 1)
11: Mode 3: Single-Ended 0 Forced (D+ = 0, D– = 0)
2
DFREC
Differential Receiver Bit
The state of this bit indicates the current differential value present on the D+ and D-
lines when PHYEN = 1.
0: Differential 0 signalling on the bus.
1: Differential 1 signalling on the bus.
1
Dp
D+ Signal Status.
This bit indicates the current logic level of the D+ pin.
0: D+ signal currently at logic 0.
1: D+ signal currently at logic 1.
0
Dn
D– Signal Status.
This bit indicates the current logic level of the D- pin.
0: D– signal currently at logic 0.
1: D– signal currently at logic 1.