Re: [ECOS] Re: unaligned half-word flash memory access on a EB55/AT91

[Andrew Lunn <andrew@lunn.ch>]

On Sat, May 07, 2005 at 10:26:57AM +0200, Marcel Ovidiu Achim wrote:
> Andrew Lunn schrieb:
> 
> >On Fri, May 06, 2005 at 08:51:17PM +0200, Marcel Ovidiu Achim wrote:
> > 
> >
> >>Hi all,
> >>
> >>I am using eCos on an Atmel EB55 board. For an application I need to
> >>store data into the on board flash device. My compiled code seams to
> >>do an unaligned access to the on board flash which is enabled by the
> >>NCS0 line.
> >>
> >>This is a very simple code for a better understanding.
> >>
> >>// Set the EBI_CSR0 register for 16 bit access etc.
> >>HAL_WRITE_UINT32(0xFFE00000, 0x010030A1);
> >>
> >>// Write 0xAA to address 0x555 of into the flash device.
> >>// Note: this is not the whole prog. seq.
> >>HAL_WRITE_UINT16(0x01000000 + 0x555, 0xAA);
> >>  
> >
> >
> >I don't think this is allowed. You have to do 16 bit accesses on 16
> >bit aligned addresses. Maybe you want to do:
> >
> >HAL_WRITE_UINT8(0x01000000 + 0x555, 0xAA);
> >HAL_WRITE_UINT8(0x01000000 + 0x556, 0x00);
> >
> >which will acheive the same but will do it in a legal way.
> >
> >       Andrew
> >
> > 
> >
> 
> Your sugestion drives the NCS0 line twice and again the access is not 
> alligned
> (both read and write of the AT91 starts from A0 instead of A1). Since 
> the memory cells of the flash
> device are 16 bit long, while writing 0x556 means also writng to another 
> cell instead
> of 0x555.
> 
> Please give more advice.

How do you have the MMU setup for that area of memory?

        Andrew

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