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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Best representation for spares
Date: Sun, 16 Feb 2014 20:50:33 +0200
Organization: Tidorum Ltd
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Date: 2014-02-16T20:50:33+02:00
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On 14-02-16 18:26 , Rego, P. wrote:
> On Sunday, February 16, 2014 10:40:11 AM UTC-3, Rego, P. wrote:
>> I did not get. Is is better to use
>> Auxiliary_Peripherals_Register_Map: 
>>    Auxiliary_Peripherals_Register_Map_Type 
>>       := (others => <>);
>> or just initialize in system initialization?
>> (or both?)
> 
> Now I guess RPi board talked to me :-)
> I tried to use both approaches joint and separately, and in all
> initialization attempts from definition I got an 
> 
> raised STORAGE_ERROR : stack overflow (or erroneous memory access)
> 
> which only was resolved when I removed both initializations
> kinds. So it seems to be safer to initialize the registers
> in run-time, inside a specific initialize procedure.

Oho, Raspberry Pi? Probably not bare-board, so which OS?

In general OSes, I/O registers are typically *not* directly accessible
from user processes, so the exception is probably coming from an
erroneous memory access. That is, the address of the MMIO register is
not accessible to your process, which runs in its own virtual memory
address space.

If this is the reason for the error, it will happen also if you use an
assignment statement to set the register from some initialization procedure.

You either have to use a driver, or take some action to map the MMIO
address into your process space. I don't know how this works on the RPi.
I found some advice at
https://sites.google.com/site/semilleroadt/raspberry-pi-tutorials/gpio;
I assume some moore googling will bring lots of info.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
      .      @       .