Re: [uCsimm] Downloading kernel via e-net?

From: Tom Walsh (tom@cyberiansoftware.com)
Date: Fri Aug 18 2000 - 20:41:00 EDT


Robert Poor wrote:
>
> I've been having a grand time playing with my uCsimm. In the
> interests of faster dev cycles:
>
> [1] Is it possible to load and execute image.bin from the uCsimm
> RAM rather than committing it to flash? If so, how do I know
> what address to give to goram?

I don't see much savings / increase in performance of the kernel by
executing in DRAM, with the Chip Select for the Flash running at 0 wait
States, your 90 ns. Flash should cook along without delays. When
running inside of DRAM, you have the slight possibility of having a
collision between the microcode prefetch unit and the DRAM controller
demanding the busses... I have not looked at this, but would expect
this not to be a problem as the internal integration between the bus
logics should have prediction abilities / resolver to avoid such
contentions.

> [2] Is there an easy way to load image.bin via e-net? I have my
> dev directory NFS mounted on /usr (that's wonderful)?

Theoretically possible, dangerous as you might lose control of the Flash
programming algorthim and wipe your existing Flash clean, but you
*could* malloc() a BIG section of DRAM, load the image into that, then
launch a Flash programmer code. BUT, you would need to have a Linux to
burn a Linux, lose a working Linux, you lose the ethernet network layer,
and then you would have to revert back to your ucsimm loader + minicom.

Question is, would it be more useful to place smaller code (like RTAI)
into a dedicated Flash sector, then have the kernel install this code
(from within crt0_r*m.S) when starting the system, this would make the
cut / try of new stuff run a much faster development cycle. In order to
do this, you would have to write your own Flash loader to place this
code into that sector, no big deal to do this, I do something similar
with the EZ328SIMM. You may have the loader capability already present
in your uCsimm stuff? Doesn't the uCsimm loader use the XModem in
minicom to upload code, and isn't that placed / burned at a specific
address??

TomW

-- 
Tom Walsh - WN3L - Embedded Systems Consultant
'www.openhardware.net', 'www.cyberiansoftware.com'
"Windows? No thanks, I have work to do..."
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