[ECOS] Fwd: Packet size limit on TCP/IP stack ?

[mohanlal jangir]

> I would not totally trust that runt are not being sent. Only a few
> network cards will actually tell you about them. Most silently discard
> them.
I think you are right because 82559 manual have some lines which favours
your statement. I wanted to confirm this by reading statistical counters of
82559 chip. It has one counter for packets which could not be transmitted
because of transmission underrun. The manual says, "A transmit underrun
occurs because the system bus can not keep up with the transmission. This
counter contains the number of frames that were either not transmitted or
retransmitted due to a transmit DMA underrun".
For reading the counters I tried to insert this code after call to TxMachine
{
   cyg_uint32  my_ioaddr = p_i82559->io_address;
   unsigned char stat_counters[20] = { 0x00 };
   unsigned char i;
   OUTL(VIRT_TO_BUS(stat_counters), my_ioaddr + SCBPointer);
   OUTW(CU_SHOWSTATS, my_ioaddr + SCBCmd);

   for(i = 0; i < sizeof(stat_counters); i++)
       os_printf("%02x ", stat_counters[i]);
   os_printf("\n");
}

But I was unable to read anything. It was showing all zeros. I haven't
interfaced with hardware device earlier. I thought, issuing CU_SHOWSTATS to
NIC will fill statistical counter values to address stat_counters. Could you
please help me in reading statistical counters?


> The i82558 programming manual is ( was the last time i looked) from
> the Intel web site. The i82559 is backward compatible, so you can use
> that for most of the registers.
Thanks. I have downloaded 8255X_OpenSDM.pdf and 82559 datasheet. These are
really very helpful.

> > I am running at 100Mbit/s. Again, I think this is configured in
> > i82559_configure. Please let me know how to change this.
>
> Connect your device to an old hub that only supports 10Mbit/s. The
> i82559 will then negotiate down to 10Mbit/s. You can also set a
> register in the i82559, but thats a bit harder to do.
I will try this option later. For this I have to manage suitable hub :-(

Regards
Mohanlal


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