DOC7707 datasheet(51/307 Pages) ETC1

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7707F–AVR–11/10

AT90USB82/162

Figure 9-7.

USB Reset During Operation

9.7.1

MCU Status Register –MCUSR

The MCU Status Register provides information on which reset source caused an MCU reset.

• 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.

USB Traffic

USBRSTMIN

End of Reset

Bit

–

USBRF

–

WDRF

BORF

EXTRF

PORF

MCUSR

Read/Write

R/W

Initial Value

See Bit Description

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