[En-Nut-Discussion] Ethernut 3 Ethernet not working

ml mludwig at adc-elektronik.de
Fri Nov 13 14:03:33 CET 2009


on some of my own build (Ethernut 3 based) cpu boards ethernet interface is
not working when
code is in rom. In ram it works good.  
First i thought that it might be a hardware related problem because only 2
board´s of 100 show this
error. But later on i tried to find out where it comes from. (Hard thing
because it don´t be able to
debug in rom mode)  After a bit modern debugging with my logicanalayzer i
found out that the timing
at the dm9000e nic is a bit critical. This depends on the waitstates defined 
in crtat91_rom.s.
There are only 2 (Description from harald was 4 in the 4.40 version of nut,
but 2 are set) . 
It must be 3 or more because the timing with 2 is so critical that
tolerances of the chips and 
oszillator may add so bad that the write command to the nic failed.

After changing this my boards works reliable.

In crtat91_boot.s i see that there are 4 waits defined so this will work
I see in the 4.9 version that harald has changed the crtat91_rom.s. But he
changed the comment 
to 2 waits not the the EBI define itself to 3 or 4 which will be better i

may be this helps someone else.

who learned a lot of the deeps of  ethernut and tcp while solving this
strange problem :)
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