[U-Boot-Users] possible problem in u-boot-0.2.0/cpu/mpc8xx/cpu_init.c
r.meyer at emk-elektronik.de
Wed Feb 5 12:51:18 CET 2003
After Power-On PONReset is held active for about 300ms. After that:
Page 15-7 states that there will be no clock until the PLL stabilizes.
Booting with MODCK=00 is one of the possible ways to Clock the MPC860 and
requires a 32768 Hz crystal, see page 15-7
The board is a companion to a Pin-Compatible MC68360 board which runs off a
32768 Hz crystal, too.
There was no obvious reason NOT to do it the same way for the MPC860,
but it gives you full freedom at what speeds you want to run the board
(and how much heat you want to produce, the 80MHz Version definitely needs a
The question I have put up is not whether it is usual to do it that way (we
do it for all our 8xx designs that way),
but whether it is possible to change the order in cpu_init.c generally
or whether I have to do that with a nasty #if defined(TOP860). So far I did
not need to touch any sources outside
the (new) board/emk/top860 directory, and I would prefer to keep it that way
once the port is finished, I will of course submit that directory and the
changes to MAKEALL and Makefile
(need to finish the FLASH driver, since we use ONE 16-bit wide FLASH, and
need to finish the PHY driver,
since we support auto detection of Fiber, 10/100 HD/FD with the Am974...)
> In message <012701c2cd00$d3f94ce0$6d4ba8c0 at alb.sub.de> you wrote:
> > The Processor starts with 32kHz*512,
> Did you measure the time it takes after power-on before the CPU
> executes the first instruction? This is the first system I see that
> boots like this, so I'm curious.
> Why do you do it this way?
> > I cannot find any reference in the 860UM that forbids changing the EBDF
> > the initial HRCW setting...
> It's not exactly forbidden, but U-Boot does not expect this. And no
> other board I've ever seen does it this way.
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