FEC Tx FIFO Status Register—MBAR + 0x31A8
MPC5200B Users Guide, Rev. 1
Freescale Semiconductor 14-29
14.8.1 FEC Rx FIFO Cont rol Register—MBAR + 0x318CFEC Tx FIFO Control Register—MBAR + 0x31AC
The RFIFO_CONTROL and TFIFO_CONTROL registers provide programmability of many FIFO behaviors, from last transfer granularity
to frame operation. Last transfer granularity allows the user to control when the FIFO controller stops requesting data transfers through the
FIFO alarm. When the alarm is configured as a Receive FIFO, the granularity value is the GR[2:0] value. When the alarm is configured as a
Transmit FIFO, the granularity value is four times the GR[2:0] value, or the pipeline depth. The frame bit of the control register provides a
capability to enable and control the FIFO controller’s ability to view data on a packetized basis. The FIFO controller also has the
programmable capability to not request attention after it has received a complete frame until Ethernet has reported completion of transmission.
Frame mode supersedes the FIFO granularity bits, through the assertion of a hardware signal to BestComm.
10 UF UF FIFO Underflow – Sticky, Write To Clear
This bit signifies the read pointer has surpassed the write pointer. This bit will remain set until
this bit of the FIFO status register has been written with a 1.
11 OF OF FIFO Overflow – Sticky, Write To Clear
This bit signifies the write pointer has surpassed the read pointer. This bit will remain set until
this bit of the FIFO status register has been written with a 1.
12 FR FR Frame Ready – Read Only
The FIFO has requested attention because there is framed data ready. All complete frames
must be read from the FIFO to clear this alarm. This alarm will only be asserted while in
frame mode.
13 Full Full Alarm – Read Only
The FIFO has requested attention because it is full. The FIFO must be read to clear this
alarm.
14 Alarm FIFO Alarm – Read Only
The FIFO has requested attention because it has determined an alarm condition. The
specific alarm condition detected is dependent upon the FIFO direction (Transmit or
Receive); if it is a Transmit FIFO, then the FIFO alarm output pin provides indication of a low
level, asserting when there is less than alarm bytes of data remaining in the FIFO, and
deasserting when there are less than 4* granularity free bytes remaining. When the FIFO is
configured to Receive, the FIFO alarm provides high level indication, asserting when there
are less than alarm bytes free in the FIFO, and deasserting when there are less than
granularity bytes of data remaining. This signal can be cleared by reading or writing (as
appropriate) the FIFO, or manipulating the FIFO pointers.
15 Empty Empty – Read Only
The FIFO has requested attention because it is empty. The FIFO must be written to clear this
alarm.
16:31 --- Reserved
Bits Name Description