21.4.30 USB0AEC: USB0 Advanced Energy Control
Bit
7
6
5
4
3
2
1
0
Name
LEMSTA
XCVRMD
OSCMD
Reserved
LEMCN
Access
R
RW
RW
R
RW
Reset
0
0
0x0
0x0
0x0
SFR Page = 0x20; SFR Address: 0xB2
Bit
Name
Reset
Access Description
7
LEMSTA
0
R
Low Energy Mode Status.
This bit indicates whether low energy mode mode is active, due to current USB bus conditions.
Value
Name
Description
0
OFF
The USB peripheral is in normal mode.
1
ON
The USB peripheral is in a low energy mode.
6
XCVRMD
0
RW
Transceiver Mode.
This bit controls how the USB transceiver hardware is affected by low energy mode.
Value
Name
Description
0
LOW_POWER
The USB transceiver is selectively put into a lower power state when
low energy mode is active.
1
NORMAL_POWER
The USB transceiver is not affected by low energy mode.
5:4
OSCMD
0x0
RW
Low Energy Mode Oscillator Control.
This field configures how LE mode affects USB clocking. It should be set to 00 in most applications.
Value
Name
Description
0x0
OSC_GATED_SUS-
PEND
The USB clock source is selectively gated by LE mode, and the High-
Frequency Oscillator (HFOSC1) is suspended if possible.
0x1
OSC_GATED
The USB clock source is selectively gated by LE mode. There is no ef-
fect to HFOSC1.
0x3
OSC_ON
LE mode has no effect on either the USB clock or HFOSC1.
3:2
Reserved
Must write reset value.
1:0
LEMCN
0x0
RW
Low Energy Mode Control.
The LEMCN bits control when Low Energy Mode is used. It is recommended that this field is set to 11 when LE mode is
used.
Value
Name
Description
0x0
DISABLED
LE mode is disabled.
0x1
IDLE
LE takes effect only during idle bus times.
0x2
NAK_OUT
LE takes effect only during NAKed OUT packets.
0x3
ALL
LE takes effect during idle bus and NAKed OUT packets.
EFM8UB3 Reference Manual
Universal Serial Bus (USB0)
silabs.com
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