MPC8280 datasheet(954/1386 Pages) FREESCALE

954 / 1386 page

Fast Communications Controllers (FCCs)

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

30-16

Freescale Semiconductor

7. Initialize the required values for this FCC in its parameter RAM.

8. Clear out any current events in FCCE, as needed.

9. Write the FCCM register to enable the interrupts in the FCCE register.

10. Write the SCPRR_H to configure the FCC interrupt priority.

11. Clear out any current interrupts in the SIPNR_L, if preferred.

12. Write the SIMR_L to enable interrupts to the CP interrupt controller.

13. Issue an INIT TX AND RX PARAMETERS command (with the correct protocol number).

14. Set GFMR[ENT] and GFMR[ENR].

The first RxBD’s empty bit must be set before the INIT RX COMMAND. However TxBDs can have their

ready bits set at any time. Notice that the CPCR does not need to be accessed after a power-on reset until

an FCC is to be used. An FCC should be disabled and reenabled after any dynamic change in its parallel

I/O ports or serial channel physical interface configuration. A full reset using CPCR[RST] is a

comprehensive reset that also can be used.

30.10 FCC Interrupt Handling

The following describes what usually occurs within an FCC interrupt handler:

1. When an interrupt occurs, read FCCE to determine interrupt sources. FCCE bits to be handled in

this interrupt handler are normally cleared at this time.

2. Process the TxBDs to reuse them if the FCCE[TX,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 FCC. 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.

3. Extract data from the RxBD if FCCE[RX, RXB, or RXF] is set. If the receive speed is fast or the

interrupt delay is long, the FCC 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 E set. Because the FCC prefetches BDs, the

BD table must be big enough such that always there will be another empty BD to prefetch.

4. Clear FCCE.

5. Continue normal execution.

30.10.1 FCC Transmit Errors

There are four errors in the FCC transmitter that make it necessary for software to act on the transmitter

before correct operation can continue. The errors are as follows:

•

CTS-lost indication in HDLC transmitter (use re-initialization procedure)

•

Underrun in any of the serial FCC transmitter protocols (use re-initialization procedure)

•

Late collision in fast Ethernet transmitter (use recovery or re-initialization procedure)

•

Expiration of retry limit in fast Ethernet (use recovery or re-initialization procedure)

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