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Altera_Forum's avatar
Altera_Forum
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8 years ago

memory initializing into 16-words per line instead of 4 words (initialize from ihex)

This seems strange. In ModelSim (and Quartus, I beleive), our *.hex files initialize what seems to be in 16-word blocks rather than 4-word blocks. I've attached a screenshot each.

As you can see, the first two lines of the ihex file is:

[word0], [word1], [word2], [word3]

BUT the memory appears as:

[word0], [word1], [word2], [word3], [0x0000], [0x0000], [0x0000], [0x0000], [0x0000], [0x0000], [0x0000], [0x0000], [0x0000], [0x0000], [0x0000], [0x0000]

Basically, for each line in the ihex file (4 words), there are 16 words written to memory. These 16 are the original 4 words, then 12 words of zeros.

Has anyone else had this problem or know how to fix it?

** Update: In Quartus, this seems to be resolved by Assignments>Settings>Compilation Process Settings> More Settings> Reading or writing Hexadecimal(.hex) File in byte addresable mode On. However, this option is not available in ModelSim.

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    8 years ago

    There seems to be a discrepancy in words size, byte versus double word addressing. Please show the memory definition.

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    8 years ago

    FvM,

    I've attached both the RAM generation file and the Intel hex file...

    One solution we thought of is to simply skip 12 addresses at a time:

    assign reduced_addr = {addr[31:4],2'b0,addr[3:2]}; // this converts 16-word addressing into 4-word addressing

    This works, but we lose 75% of available memory doing so.