[ECOS] Re: RAM vs. ROMRAM question

Gary Thomas gary@mlbassoc.com
Tue Oct 31 17:47:00 GMT 2006

Grant Edwards wrote:
>>>> What is the exact complaint you are getting?
>>> That being a ROM monitor is a conflict with RAM startup but not
>>> with ROMRAM startup.
>> ecos.ecc:
>> cdl_option CYGSEM_HAL_ROM_MONITOR {
>>      # Flavor: bool
>>      # No user value, uncomment the following line to provide one.
>>      # user_value 0
>>      # value_source default
>>      # Default value: 0
>>      # Requires:  CYG_HAL_STARTUP == "ROM" || CYG_HAL_STARTUP == "ROMRAM"
> Exactly.  
> It's been stated that it doesn't make sense for
> CYGSEM_HAL_ROM_MONITOR to be set for RAM startup because
> RedBoot would be loading apps into the RAM where RedBoot itself
> is running.  
> ROMRAM RedBoot runs in the exact same memory locations as RAM
> RedBoot, so why doesn't that reasoning apply to ROMRAM startup?

But it doesn't - at least not on any platforms I use/maintain.
ROMRAM *anything* typically loads in lowest memory, e.g. 0x00000000 on up.
RAM *anything* then loads somewhere past the memory used by a ROMRAM RedBoot.
For example, on most PowerPC platforms, ROMRAM code will be loaded at 0x0
and RAM code will load at something like 0x80000.  This includes the space
for the ROMRAM RedBoot and all of it's workspace.

Notice that the quoted CDL option is platform defined.  If you want
to have a platform that allows CYGSEM_HAL_ROM_MONITOR in RAM mode, I
don't see why it wouldn't work.

Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world

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