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

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"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. 

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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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