AT90USB82/162
Figure 9-7. USB Reset During Operation
CC
End of Reset
tUSBRSTMIN
DP
USB Traffic
USB Traffic
DM
9.7.1
MCU Status Register –MCUSR
The MCU Status Register provides information on which reset source caused an MCU reset.
Bit
7
–
R
0
6
–
R
0
5
4
3
2
1
0
USBRF
–
WDRF
R/W
BORF
R/W
EXTRF
R/W
PORF
R/W
MCUSR
Read/Write
Initial Value
R
0
R/W
See Bit Description
• Bit 7-6 – Res: Reserved Bit
These bits are reserved and will always read as zero.
• Bit 5 – USBRF: USB Reset Flag
This bit is set if a USB Reset occurs. The bit is reset by a Power-on Reset, or by writing a logic
zero to the flag.
• Bit 4– Res: Reserved Bit
This bit is reserved.
• Bit 3 – WDRF: Watchdog Reset Flag
This bit is set if a Watchdog Reset occurs. The bit is reset by a Power-on Reset, or by writing a
logic zero to the flag.
• Bit 2 – BORF: Brown-out Reset Flag
This bit is set if a Brown-out Reset occurs. The bit is reset by a Power-on Reset, or by writing a
logic zero to the flag.
• Bit 1 – EXTRF: External Reset Flag
This bit is set if an External Reset occurs. The bit is reset by a Power-on Reset, or by writing a
logic zero to the flag.
• Bit 0 – PORF: Power-on Reset Flag
This bit is set if a Power-on Reset occurs. The bit is reset only by writing a logic zero to the flag.
To make use of the Reset Flags to identify a reset condition, the user should read and then
Reset the MCUSR as early as possible in the program. If the register is cleared before another
reset occurs, the source of the reset can be found by examining the Reset Flags.
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7707D–AVR–07/08
ATMEL [ ATMEL ]
