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Altera_Forum's avatar
Altera_Forum
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16 years ago

Compressed bit streams???

What's the deal with the compressed bit streams in Quartus?

I have "Generate Compressed Bitstreams" option turned on in Settings/Device/Device and Pin Options/Configuration.

I have the configuration mode set as Active Serial. What is puzzling is that the pof file size is almost twice that of the sof. Why is this?

I even tried to generate a compressed pof file using the File/Convert Programming File tool as shown in the configuration section (chapter 9) of the arria ii gx handbook. But it also generates the same sized pof file.

TIA.

6 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    The POF file size (the same with *.jic JTAG indirect programming file) is defined by the memory capacity of the selected configuration device. In case of auto selection, Quartus uses the AS device, that's needed for an uncompressed file. The unused part is zero filled. The *.sof file in constrast is never compressed.

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    I am guessing this would be the uncompressed .pof. Shouldn't the compressed .pof be smaller?

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    An uncompressed *.pof can't be smaller than the specified configuration file size for a specific device, a compressed file usually is. Try different EPCS types for your design and you'll see.

    As an example, EP3C16 or EPC3C25 configuration only fits an EPCS4 when compressed.
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    Thanks. It seems like my problem at present is that for some reason Quartus just doesn't compress the pof file. Even though I ask it to compress it.

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    If you are using the programming file conversion tool, compression has to be set in the tool itself while the compression option in the device assigments is valid for the programming files generated by the Quartus assembler.

    As said, the *.pof file size doesn't tell, if the file is compressed.