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RE: Network connection
It is OK to let ETRAX generate the 25MHz clock. Please note that the BCM 5201
and BCM 5221 pinout differs. The 25MHz clock input shall go to XTALI on 5201 but
to REF_CLK on 5221. If you want your hardware to be able to do network boot,
you must make sure that the 25 MHz clock is stable when the transceiver reset_ is
deasserted. This is handled as you can se in the devboard_lx circuit diagram by
using 2 reset circuits, so that the Ethernet transceiver gets a "delayed" reset.
If you are not going to use network boot the transceiver reset can be generated from ETRAX
using a GPIO signal, software support for this has to be made off course.
The clock is activated after reset in network boot mode. In normal boot mode the clock
is activated by register settings, this is handled by the linux kernel so it's nothing you
have to worry about.
From: Rob Gaddi [mailto:email@example.com]
Sent: den 26 juni 2001 23:52
Subject: Network connection
Building a board based on the ETRAX 100LX, but due to parts availability
I'm using the Broadcom 5221 instead of the 5201. The 5221 uses an
external 25MHz clock instead of the internal one the 5201 uses. I
noticed in section 20.8 of the programmer's manual that pin U12 can be
used to output a 25 MHz clock, or a few other things. How do I make it
send the clock signal, and does anyone know whether this should do the