Interrupt Handling - Freescale Semiconductor MPC8313E Family Reference Manual

Size [Octets] Description
2 MAC opcode
2 MAC parameter
2 Extended MAC
40
4
If flow-control mode is enabled (MACCFG1[Rx_Flow] is set) and the receiver identifies a pause-flow
control frame, transmission stops for the time specified in the control frame. The controller completes any
frame in progress before stopping transmission and does not commence counting the pause time until
transmit is idle. During a pause, only a control frame can be sent (TCTRL[TFC_PAUSE] is set). Normal
transmission resumes after the pause timer stops counting, or resumes immediately if a pause frame with
a zero time-out is received. If another pause-control frame is received during the pause, the period changes
to the new value received.

15.6.2.10 Interrupt Handling

The following describes what usually occurs within a eTSEC interrupt handler:
• If an interrupt occurs, read IEVENT to determine interrupt sources. IEVENT bits to be handled in
this interrupt handler are normally cleared at this time. There are three kinds of interrupts:
— Receive data frame interrupts, when bits RXB or RXF in IEVENT are set
— Transmit data frame interrupts, when bits TXB or TXF in IEVENT are set
— Error, diagnostic, and special interrupts (all bits in IEVENT other than RXB, RXF, TXB, or
TXF)
• Process the TxBDs to reuse them if the IEVENT[TXB, TXF or TXE] were set. Consult register
bits TSTAT[TXF0–TXF7] to determine which TxBD rings gave rise to the transmit interrupt in the
case of TXF. If the transmit speed is fast or the interrupt delay is long, more than one transmit buffer
may have been sent by the eTSEC; 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.
• Obtain data from RxBD rings if IEVENT[RXC, RXB or RXF] is set. Consult register bits
RSTAT[RXF0–RXF7] to determine which RxBD rings gave rise to the receive interrupt in the case
of RXF. If the receive speed is fast or the interrupt delay is long, the eTSEC may have received
more than one RxBD; 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 E set.
Because the eTSEC pre-fetches BDs, the BD table must be big enough so that there is always
another empty BD to pre-fetch, otherwise a BSY error occurs.
MPC8313E PowerQUICC II Pro Integrated Processor Family Reference Manual, Rev. 3
Freescale Semiconductor
Table 15-144. Flow Control Frame Structure (continued)
Value
00-01
parameter
Reserved —
FCS
Enhanced Three-Speed Ethernet Controllers
Comment
Pause command
Pause time as defined by the PTV[PT] field. The pause
period is measured in pause_quanta, a speed
independent constant of 512 bit-times (unlike slot time).
The most-significant octet is transmitted first.
Pause time extended as defined by the PTV[PTE] field.
The most significant octet is transmitted first.
—
Frame check sequence (CRC)
15-155