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Altera_Forum's avatar
Altera_Forum
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14 years ago

Ddr sdram

Hi,

Can someone tell me how to read and write data to specified memory address like 0x02000001 and so on.

I'm programming with Eclipse and I declare an array like:

unsigned char buff[256][512];

I wanna write data in this array and after that I want to take the values from memory, so I have to know memory range.

Can anyone help me with this?

Regards

Kycas

6 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    You can use pointers for that. You can assign an address to a pointer.

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    Thank You for an answer

    Can you show an example how to do with pointers, I'm not very good at C and I dont know how to use these pointers :)

    Or maybe it will be Ok if I just use IOWR_8DIRECT() for example?
  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    Something like this should work:

    char *mypointer = 0x02000001;
*mypointer = ...;

    You can also use the IORD/IOWR macros. The main difference between pointers and the IORD/WR macros is that a pointer access can use the data cache, while the IO macros will always bypass it.
  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    Great!

    One more thing, should I just put all array of data with one IOWR() function, or should I make a loop and write byte by byte to memory?
  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    It depends on your needs. Doing a 32-bit operation with a IOWR() or an (unsigned) int pointer will give you better performance than writing byte per byte.

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    I think the same thing. I have char type data, so I'll use IOWR_8DIRECT() with a loop.

    Oh and one more thing, if I declare some variables with value for example:

    float c[3][3] = {{1,1,1},

    {1,1,1},

    {1,1,1}};

    I think that this "c" will be put in SDRAM and if I write date with IOWR() function from the beginning of memory lets say. Won't the data that I want to write overlap the declared data "c"?

    Its kind of confusing with this to me...