Freescale Semiconductor MCF5480 - Manual (Page 890)

MCF548x Reference Manual, Rev. 3
29-16 Freescale Semiconductor
29.2.2.7 USB Application Interrupt Status Register (USBAISR)
The USBAISR contains information regarding the source of a USB interrupt event. Interrupt sources may
be masked in the USBAIMR. The application must clear all interrupt bits when necessary as they do not
clear automatically. Clear the bits by writing zeros.
There is only one USBAISR to record all interrupt events for multiple endpoints. It is the responsibility of
the application software’s interrupt service routine (ISR) to read the contents of the EPINFO register to
determine the interrupting endpoint number and direction.
Table 29-7. USBIMR Field Descriptions
Bits Name Description
31—8 — Reserved, should be cleared.
7 MSOF Missed start of frame interrupt.
0 Missed start of frame interrupts enabled.
1 Missed start of frame interrupts disabled.
6 SOF Start of frame interrupt.
0 Start of frame interrupts enabled.
1 Start of frame interrupts disabled.
5 RSTSTOP Reset stop. This indicates the end of reset signalling on the USB.
0 Reset signalling stopped interrupts enabled.
1 Reset signalling stopped interrupts disabled.
4 UPDSOF Updated start of frame. This indicates that the current SOF interrupt was the result of the USB
having to update its internal frame number due to a missing SOF packet.
0 Updated start of frame interrupts enabled.
1 Updated start of frame interrupts disabled.
3 RES Resume. This is used to indicate a state change from suspend to resume in the USB. This bit only
indicates the change from suspended to active mode. Clearing the interrupt has no effect on the
actual state of the USB.
0 Resume interrupts enabled.
1 Resume interrupts disabled.
2 SUSP Suspend. This is used to indicate a suspend state in USB. This bit only indicates the change from
active to suspended mode. Clearing the interrupt has no effect on the actual state of the USB.
0 Suspend interrupts enabled.
1 Suspend interrupts disabled.
1 FTUNLCK Frame timer lost lock. This is used to indicate when the internal frame timer has lost its lock on the
SOF packet sequences. This condition occurs when three consecutive SOF packets are missed
by the core.
0 Frame timer lost lock interrupts enabled.
1 Frame timer lost lock interrupts disabled.
0 ISOERR Isochronous error. This indicates that a high-speed, high-bandwidth isochronous OUT endpoint
detected a PID sequencing error.
0 Isochronous error interrupts enabled.
1 Isochronous error interrupts disabled.