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Re: Code or SWI to read word of logical memory?

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"neil f" <news@anf.nildram.co.uk> wrote in message 
news:iro5et$3t2$1@speranza.aioe.org...
>
> "Theo Markettos" <theom+news@chiark.greenend.org.uk> wrote in message 
> news:8Oh*fa+Dt@news.chiark.greenend.org.uk...
>> neil f <news@anf.nildram.co.uk> wrote:
>>> I need to read and write a word or two of memory during execution of a
>>> program. Is it possible to do this via a snippet of assembler from 
>>> Basic?
>>> Alternatively, is there a SWI that I can call when necessary for the
>>> read/write operation? I've mapped in the memory locations I'm interested 
>>> in
>>> using OS_Memory 13, so I can supply a logical address to a routine.
>>
>> Do you mean physical memory?
>>
>> Logical memory = what the programmer sees (aka virtual memory on systems
>> with page files)
>> Physical memory = how the memory chips are actually connected
>>
>> If you really mean logical memory, you can either just read it normally
>> (PRINT !address%) or else drop into supervisor mode to access memory that
>> user mode doesn't have read permissions for (see OS_EnterOS).
>>
>> Note that on RISC OS applications share logical address space (they all
>> think they start at &8000) so you have to be sure that the right 
>> application
>> is paged in.
>>
>> Theo
>
> Hi Theo. I'm messing around with a Beagle XM. I started out looking at 
> just GPIO access but after a few days absorbing the TRM etc I'm finding 
> all sorts of memory mapped registers I'd like prod and play with.
>
> Peter xxx and Tank have been knocking up some useful module code, but it's 
> limited to specific register ranges and all very well behaved. It won't 
> let me stray 'off piste', which is what I'd like to do to really get to 
> know what the various interfaces can provide. All I need for that is to 
> map in some physical address ranges to logical ones (which OS_Memory 13 
> seems to be designed for) and then have a read routine and a write routine 
> that can access any register in the mapped in range.
>
> So I'd like to map register X physical to logical address, then supply 
> that logical address to a read or write routine to monitor and manipulate 
> various XM I/O processes.
>
> I've got as far as mapping physical registers to logical addresses, which 
> seems to work fine. But any moves to read from those addresses just 
> produce data aborts at the moment. Even just using plain SYS"OS_EnterOS" 
> followed straight away with SYS"OS_LeaveOS" gives a data abort. I would 
> have thought that was practically a NOP but it still throws up an error.
>
> -Neil.

Sorry, I meant SWI "OS_EnterOS" in the above of course.

E.g the following gives a data abort when run:

DIM code% 100
FOR pass%=0 TO 3 STEP 3
P%=code%
[
OPT pass%
SWI "OS_EnterOS"
SWI "OS_LeaveOS"
]
NEXT pass%
CALL code%

Shouldn't it just do nothing?

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Code or SWI to read word of logical memory? "neil f" <news@anf.nildram.co.uk> - 2011-05-27 09:34 +0100
  Re: Code or SWI to read word of logical memory? Theo Markettos <theom+news@chiark.greenend.org.uk> - 2011-05-27 11:42 +0100
    Re: Code or SWI to read word of logical memory? "neil f" <news@anf.nildram.co.uk> - 2011-05-27 13:29 +0100
      Re: Code or SWI to read word of logical memory? "neil f" <news@anf.nildram.co.uk> - 2011-05-27 13:47 +0100
        Re: Code or SWI to read word of logical memory? "neil f" <news@anf.nildram.co.uk> - 2011-05-27 14:36 +0100
          Re: Code or SWI to read word of logical memory? Theo Markettos <theom+news@chiark.greenend.org.uk> - 2011-05-28 00:20 +0100
            Re: Code or SWI to read word of logical memory? "neil f" <news@anf.nildram.co.uk> - 2011-05-29 21:31 +0100
              Re: Code or SWI to read word of logical memory? Theo Markettos <theom+news@chiark.greenend.org.uk> - 2011-05-29 23:40 +0100
            Re: Code or SWI to read word of logical memory? Jeremy Nicoll - news posts <jn.nntp.scrap007@wingsandbeaks.org.uk> - 2011-06-01 02:07 +0100
              Re: Code or SWI to read word of logical memory? Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-06-01 04:24 +0200
          Re: Code or SWI to read word of logical memory? Tank <webmaster@tankstage.co.uk> - 2011-05-28 06:54 +0100
            Re: Code or SWI to read word of logical memory? "neil f" <news@anf.nildram.co.uk> - 2011-05-28 22:36 +0100
              Re: Code or SWI to read word of logical memory? Tank <webmaster@tankstage.co.uk> - 2011-05-29 08:38 +0100

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