[ECOS] Re: RAM vs. ROMRAM question

[Grant Edwards <grante at visi dot com>]

In gmane.os.ecos.general, you wrote:

>>> 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?
>
> No. ROMRAM RedBoot loads to low RAM, usually the bottom 128K. RAM
> applications and RAM RedBoot would load above 128K.

Oh.  That's not the way the NOIS2 HAL is set up.  AFAICT, RAM
and ROMRAM RedBoots are pretty much identical.  All of the
sections load at the same place (starting at the bottom of
RAM). The only difference seems to be a "bootloader" .srec file
that's pulled out of the air and tacked onto a ROMRAM .srec
file.

I'll have to build some "normal" apps to see where they load.

> ROM RedBoot would keep its code in ROM but put its data below
> 128K, and the rest of memory up to 128K would be unused. JTAG
> RedBoot would load in the bottom 128K just like ROMRAM.

OK.  Thanks for the clarification.

> Under normal circumstances a RAM RedBoot is only needed when
> RedBoot is normally run out of ROM, and then only to enable
> the ROM image to be reprogrammed. So, it is not necessary for
> a RAM RedBoot to be capable of loading and debugging an
> application. Hence CYGSEM_HAL_ROM_MONITOR is disabled.

That makes sense. I guess the HAL Altera provides for the NIOS2
is just, uh, abnormal.

-- 
Grant Edwards                   grante             Yow!  Do I hear th'
                                  at               SPINNING of various
                               visi.com            WHIRRING, ROUND, and WARM
                                                   WHIRLOMATICS?!

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