253
8331B–AVR–03/12
Atmel AVR XMEGA AU
FLAGSACLR. Both memory locations will provide the same result when read, and writing zero to
any bit location has no effect.
• Bit 7 – SOFIF: Start Of Frame Interrupt Flag
This flag is set when a start of frame packet has been received.
• Bit 6 – SUSPENDIF: Suspend Interrupt Flag
This flag is set when the bus has been idle for 3ms.
• Bit 5 – RESUMEIF: Resume Interrupt Flag
This flag is set when a non-idle state has been detected on the bus while the USB module is in
the suspend state. This interrupt is asynchronous, and is able to wake the CPU from sleep
modes where the system clock is stopped, such as power-down and power-save sleep modes.
• Bit 4 – RSTIF: Reset Interrupt Flag
This flag is set when a reset condition has been detected on the bus.
• Bit 3 – CRCIF: Isochronous CRC Error Interrupt Flag
This flag is set when a CRC error has been detected in an incoming data packet to an isochro-
nous endpoint.
• Bit 2 – UNFIF: Underflow Interrupt Flag
This flag is set when the addressed endpoint in an IN transaction does not have data to send to
the host.
• Bit 1 – OVFIF: Overflow Interrupt Flag
This flag is set when the addressed endpoint in an OUT transaction is not ready to accept data
from the host.
• Bit 0 – STALLIF: STALL Interrupt Flag
This flag is set when the USB module has responded with a STALL handshake to either an IN or
an OUT transaction.
20.13.12 INTFLAGSBCLR/INTFLAGSBSET – Clear/Set Interrupt Flag eegister B
This register is mapped into two I/O memory locations, one for clearing (INTFLAGSBCLR) and
one for setting (INTFLAGSBSET) the flags. The individual flags can be set by writing a one to
their bit locations in INFLAGSBSET, and cleared by writing a one to their bit locations in INT-
FLAGSBCLR. Both memory locations will provide the same result when read, and writing zero to
any bit location has no effect.
Bit
7
6
5
4
3
2
1
0
SOFIF
SUSPENDIF
RESUMEIF
RESETIF
CRCIF
UNFIF
OVFIF
STALLIF
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
–
–
–
–
–
–-
TRNIF
SETUPIF
Read/Write
R
R
R
R
R
R
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0