Digi Rabbit 5000, User Manual

Page: 264 / 414

264 Rabbit 5000 Microprocessor User’s Manual
22.3.1 Setup
The following steps explain how to set up Network Port B.
1. Write the interrupt vector for the interrupt service routine to the external interrupt table.
2. Select the desired interrupts and interrupt priority by writing to NBCSR.
3. Select the MII interface settings by writing to NBMCFR, NBMRAR, and NBMPAR.
4. Select the desired configuration of transmit and receive operation by writing to
NBTCR, NBTESR, and MBRCR.
5. Write the device’s physical MAC address to the physical address (NBPAxR) and
station address registers (NBSAxR).
6. If desired, write to the multicast filter registers (NBMFxR) to generate a multicast filter.
7. Select other options in the configuration registers NBCFxR, NBGxR, NBRMR,
NBCWR, and NBFLxR.
8. Enable the network port transmitter by writing to NBTCR.
9. Enable the network port receiver by writing to NBRCR.
22.3.2 Transmit
The following steps explain how to transmit an Ethernet packet.
1. Set up a DMA buffer descriptor that will read the packet data from memory and write it
to NBDR. Write the buffer descriptor’s address to the DMA’s initial address registers
(see
Chapter 21 for more information).
2. Enable the DMA transfer by auto-loading the buffer.
3. The packet transmission will proceed automatically. If any interrupts were enabled for
any transmitted packet events, they will occur upon completion (or error).
Note that network interrupts will occur when the data appears in the network peripheral,
but DMA interrupts will occur when the DMA transfer is complete.
22.3.3 Receive
The following steps explain how to receive an Ethernet packet.
1. Set up a DMA buffer descriptor that will read the packet data from NBDR and write it
to memory. Write the buffer descriptor’s address to the DMA’s initial address registers
(see
Chapter 21 for more information).
2. Set up a DMA interrupt to handle the packet once it has been received and copied to
memory.
3. Enable the DMA transfer by auto-loading the buffer.
4. The packet transmission will proceed automatically when data come in. When the DMA
transfer is complete, the DMA interrupt can be used to start the packet processing. The
status of the received packet is appended to the received data.