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


Andrew Lunn schrieb:

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



Well, the only way to set the memory behaviour that I konw is to configure the EBI_CSR0 register.
I set it up as follows.


// Set the EBI_CSR0 register for 16 bit access etc.
HAL_WRITE_UINT32(0xFFE00000, BA_0x010 | CSEN | EBI_BAT_BYTE_SELECT | EBI_TDF_0 | 4MB_PAGE | WSE | EBI_NWS_1 | EBI_DBW_16);







--
Mit freundlichen Grüssen / Best regards

Marcel Ovidiu Achim

OVIDIUS Ingenieurbüro
Vogelsangstr. 76
70197 Stuttgart/Germany

Tel.: +49 (0)711 62 03 600
Mobil: +49 (0)177 69 070 59
email: marcel.achim@ovidius-ib.de


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