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Rabbit 4000 Microprocessor User’s Manual
20.3 Operation
High-level support for TCP/IP and other protocols is beyond the scope of this manual, but
this section will describe the low-level operation of the 10Base-T Ethernet peripheral.
20.3.1 Setup
The following steps explain how to set up the network port.
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 NACSR.
3. Select the desired network port pin configuration by writing to NAPCR.
4. Write the device’s physical MAC address to the physical address registers (NAPAxR).
5. Write to the multicast filter registers (NAMFxR) to generate a multicast filter.
6. Enable the network port transmitter by writing to NATCR.
7. Enable the network port receiver by writing to NARCR.
20.3.2 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 NADR. Write the buffer descriptor’s address to the DMA’s initial address registers
(see
Chapter 19 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.
20.3.3 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 NADR and write it
to memory. Write the buffer descriptor’s address to the DMA’s initial address registers
(see
Chapter 19 for more information).
2. Enable the DMA transfer by auto-loading the buffer.
3. The packet transmission will proceed automatically when data comes in. If any inter-
rupts were enabled for any received packet events, they will occur upon completion (or
error).
Note that network interrupts will occur when the data appear in the Ethernet peripheral,
but DMA interrupts will occur when the DMA transfer is complete.
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