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Ne2000: Difference between revisions
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→External Links: I'm not sure anymore if this was the NE2000 spec
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It is a good first network card to program because it follows a simple design (making it helpful for learning), they're probably dirt-cheap, and it is supported by most PC emulators. Both [[Bochs]] and [[QEMU]] provide ISA and PCI implementations.
Ne2000 is not technically a card, it is a standard that several implementors follow. The best available description of the initial standard
== Quick Overview of the NIC design ==
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The Ne2000 network card uses two ''ring buffers'' for packet handling. These are circular buffers made of 256-byte ''pages'' that the chip's [[DMA]] logic will use to store received packets or to get received packets.
Note that a packet will
bytes at the end of a page.
==== Ring Buffer ====
Two registers <tt>PSTART</tt> and <tt>PSTOP</tt> define a set of 256-byte pages in the ''buffer memory'' that will be used for the ring buffer. As soon as the DMA attempts to read/write to <tt>PSTOP</tt>, it will be sent back to <tt>PSTART</tt>
PSTART PSTOP
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Programming registers of the NE2000 are collected in ''pages''. Page 0 contains most of the ''control and status'' registers while page 1 contains physical (PAR0..PAR5) and multicast addresses (MAR0..MAR7) to be checked by the card.
Note that the same register number could have a different meaning depending whether you ''read'' or ''write'' to it. For instance, register
<pre>
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};
</pre>
=== Initialization and MAC Address ===
This wasn't exactly obvious, but by looking at the ''ne2k-pci'' module from Linux I managed to figure out how to initilize the card and read its MAC address:
nif->iobase = nif->pcidev->bar[0] & ~0x3;
outb(nif->iobase + 0x1F, inb(nif->iobase + 0x1F)); // write the value of RESET into the RESET register
while ((inb(nif->iobase + 0x07) & 0x80) == 0); // wait for the RESET to complete
outb(nif->iobase + 0x07, 0xFF); // mask interrupts
uint8_t prom[32];
outb(nif->iobase, (1 << 5) | 1); // page 0, no DMA, stop
outb(nif->iobase + 0x0E, 0x49); // set word-wide access
outb(nif->iobase + 0x0A, 0); // clear the count regs
outb(nif->iobase + 0x0B, 0);
outb(nif->iobase + 0x0F, 0); // mask completion IRQ
outb(nif->iobase + 0x07, 0xFF);
outb(nif->iobase + 0x0C, 0x20); // set to monitor
outb(nif->iobase + 0x0D, 0x02); // and loopback mode.
outb(nif->iobase + 0x0A, 32); // reading 32 bytes
outb(nif->iobase + 0x0B, 0); // count high
outb(nif->iobase + 0x08, 0); // start DMA at 0
outb(nif->iobase + 0x09, 0); // start DMA high
outb(nif->iobase, 0x0A); // start the read
int i;
for (i=0; i<32; i++)
{
prom[i] = inb(nif->iobase + 0x10);
};
// program the PAR0..PAR5 registers to listen for packets to our MAC address!
for (i=0; i<6; i++)
{
writeRegister(nif, 1, 0x01+i, prom[i]);
};
The first 6 bytes of "prom" extracted here are the MAC address.
=== Sending a Packet ===
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The following sequence is the one observed by the ''ne2k-pci'' module in linux. Note that some odd cards needs a patch (read-before-write) that isn't covered here. The ''data configuration'' is initialized at 0x49 (word transfer, 8086 byte order, dual 16bit DMA, loopback disabled). Note that the weird driver doesn't seem to use interrupts for completion notification.
#
#
#
#
#
# Packets data is now written to the
# Poll
== ISA configuration information ==
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This can be done by writing out the contents of the reset register to the reset register.
==See Also==
===External Links===
* [https://web.archive.org/web/20010612150713/http://www.national.com/ds/DP/DP8390D.pdf DP8390D/NS32490D NIC Network Interface Controller (PDF)] datasheet for the 8390 chip on the NE2000
* https://bitsavers.org/components/national/_dataBooks/1988_National_Data_Communications_Local_Area_Networks_UARTs_Handbook.pdf, early description of NE1000(?) boards (including PROM and memory map), starting on page 124 ("DP839EB Network Evaluation Board - Application Note 479")
* [https://web.archive.org/web/20091223070134/http://www.national.com/pf/DP/DP8390D.html#Documents DP8390D Additional application notes] from NatSemi
* http://www.ethernut.de/pdf/8019asds.pdf, the RTL8019 is one of the PCI-based NE2K compliant cards.
* http://www.bcgreen.com/gnu-linux/ne2k-diag.c, a diagnostic tool that needs to be inspected to see if it helps in understanding the manuals
* http://www.cs.usfca.edu/
* https://github.com/torokernel/torokernel/blob/7d6df4c40fa4cc85febd5fd5799404592ffdff53/rtl/drivers/Ne2000.pas, example of a driver for Ne2000 in Freepascal.
[[Category:Network Hardware]]
[[Category:Standards]]
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