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RE: eCos on PID ROM build + serial



On 10-Jul-2000 Dave Airlie wrote:
> 
> Hi,
>       I've managed to get a build of my application as a ROM image
> downloaded to the 16-bit Flash(I think) on the PID board however, my code
> doesn't seem to be working like it did in RAM (surprise surprise), I have
> no debug code as I need both serial ports, but I have a led switch on at
> start up, and also at a certain point after so many chars are rx'ed, these
> do switch on, but the serial is either getting incorrect data or is losing
> some due to the FLASH,
> 
> Is the FLASH much slower than RAM, would relocating interrupt handlers to
> RAM at startup be an idea? if so is it an easy to implement idea?
> 

It most likely is the case that the FLASH is slower than RAM.  It's not too
hard to add support for this - look at the "RELOCATE_TEXT_SEGMENT" macro in
   .../hal/arm/edb72xx/VERSION/include/hal_platform_setup.h

Basically, if the code is linked at one address but is running at another
(e.g. running from FLASH), this routine will copy the image from FLASH to RAM.
It worked on other platforms with similar speed problems.

Note: I haven't thought about having only the interrupt handlers in RAM.  This
probably wouldn't help much, I speculate that it's the overall interrupt->ISR->DSR
path that may be too slow.

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