MPC8540 datasheet(1200/1302 Pages) FREESCALE

1200 / 1302 page

MPC8540 PowerQUICC III Integrated Host Processor Reference Manual, Rev. 1

21-60

Freescale Semiconductor

10/100 Fast Ethernet Controller

•

Process the TxBDs to reuse them if the IEVENT[TXB] or IEVENT[TXE] were set. If the

transmit speed is fast or the interrupt delay is long, more than one transmit buffer may have

been sent by the FEC. Thus, it is important to check more than just one TxBD during the

interrupt handler. One common practice is to process all TxBDs in the interrupt handler

until one is found with R set. See Table 21-44.

•

Obtain data from the RxBD if IEVENT[RXC], IEVENT[RXB], or IEVENT[RXF] is set.

If the receive speed is fast or the interrupt delay is long, the FEC may have received more

than one receive buffer. Thus, it is important to check more than just one RxBD during

interrupt handling. Typically, all RxBDs in the interrupt handler are processed until one is

found with bit E set. Because the FEC pre-fetches BDs, the BD table must be big enough

so that there is always another empty BD to pre-fetch. See Table 21-45.

•

Clear any set halt bits in TSTAT and RSTAT registers, or DMACTRL[GTS] and

DMACTRL[GRS].

•

Continue normal execution.

Table 21-44. Non-Error Transmit Interrupts

Interrupt

Description

Action taken by FEC

GTSC

Graceful transmit stop complete: Transmitter is put into a

pause state after completion of the frame currently being

transmitted.

None

TXC

Transmit control: Instead of the next transmit frame, a control

frame was sent.

None

TXB

Transmit buffer: A TxBD, that is not the last one in the frame,

was updated.

Programmable write-with-response TxBD

to memory before setting IEVENT[TXB].

TXF

Transmit frame: A frame was transmitted and the last TxBD of

that frame was updated.

Programmable write-with-response to

memory on the last TxBD before setting

IEVENT[TXF].

Table 21-45. Non-Error Receive Interrupts

Interrupt

Description

Action taken by FEC

GRSC

Graceful receive stop complete: Receiver is put into a pause

state after completion of the frame currently being received.

None

RXC

Receive control: A control frame was received. As soon as

the transmitter finishes sending the current frame, a pause

operation is performed lasting for the duration specified in

the received pause control frame and beginning when the

frame was first received.

None

RXB

Receive buffer: An RxBD, that is not the last one of the

frame, was updated.

Programmable write-with-response RxBD to

memory before setting IEVENT[RXB].

RXF

Receive frame: A frame was received and the last RxBD of

that frame was updated.

Programmable write-with-response to

memory on the last RxBD before setting

IEVENT[RXF].

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