Memory Map/Register Definition
MCF548x Reference Manual, Rev. 3
Freescale Semiconductor 29-41
23 FAE Frame accept error. This bit indicates a frame accept error in the FIFO controller and will assert in
two scenarios. 1) The user has over-written data in a transmit FIFO for a packet (frame) that needs
to be retried. 2) The user has read data from a receive FIFO for a packet (frame) that has
subsequently been rejected. Setting this bit will cause a FIFO error condition (ERR) in the EPnISR
unless the EPnFCR[FAEMSK] bit is set. This bit will remain set until a one is written to this bit
location. This bit is inactive when the FIFO is not programmed for frame mode.
0 No frame accept error.
1 Frame accept error.
22 RXW Receive wait states. This bit indicates that the current OUT (receive) transaction from the USB
module is incurring wait states because there is not enough free space in the FIFO to allow the write
request. Even though the FIFO is not in a catastrophic state (that is, normal operation can proceed
without flushing the FIFO), this may result in data loss for the current OUT transaction. The
assertion of this bit will cause a FIFO error condition (ERR) in the EPnISR unless the
EPnFCR[RXWMSK] bit is set. This bit will remain set until a one is written to this bit location.
0 No receive wait condition.
1 Receive wait condition.
21 UF Underflow. This indicates FIFO underflow. Read pointer has passed the write pointer. Writing a one
to this bit clears the UF indicator.
0No Underflow.
1 Writing a 0 has no effect.
20 OF Overflow. This indicates FIFO overflow. Write pointer has passed the read pointer. Writing a one to
this bit clears the OF indicator.
0 No overflow.
1 Writing a 0 has no effect.
19 FR Frame ready. This read-only bit is the frame ready indicator. This bit is unused when the FIFO is not
programmed for frame mode.
0 No complete frames exist in the FIFO.
1 One or more complete frames exists in the FIFO.
18 FU FIFO full. This read-only bit is the FIFO full indicator.
0 The FIFO is not full.
1 The FIFO has requested attention because it is full. The FIFO must be read to clear this alarm.
17 ALR FIFO alarm. This read-only bit indicates that the FIFO has determined an alarm condition.
When the FIFO is configured to receive (OUT), the FIFO alarm provides high level indication, setting
when there are less than alarm bytes free in the FIFO. The alarm is cleared when the FIFO is read
so that fewer than EPnFCR[GR] bytes remain in the FIFO.
When the FIFO is configured to transmit (IN), the FIFO alarm provides low level indication, setting
when there are more than alarm bytes in the FIFO. The alarm is cleared when the FIFO is written
so that less than (4 × EPnFCR[GR]) free bytes in the FIFO.
0 Alarm not set.
1 The FIFO has requested attention because it has determined an alarm condition.
16 EMT FIFO empty. This read-only bit is the FIFO empty indicator.
0 FIFO is not empty.
1 The FIFO has requested attention because it is empty. The FIFO must be written to clear this
alarm.
15–0 Reserved, should be cleared.

Table 29-41. EPnFSR Field Descriptions

Bits Name Description