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Altera_Forum's avatar
Altera_Forum
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14 years ago

How to use the cyclone iii internal memory in ROM mode?

Hi, I would like to ask the next question...

According to Cyclone iii Device Hand Book, it is possible to use the internal M9K memory as ROM memory (Page 35). I'm interested to save the data after the circuit's shut down, and use it after power up. There is no explanation or waveform attached how to use the ROM mode. How can I use the memory directly from the source code written by me?

thanks a lot

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    It is impossible to save data in FPGA and keep it after power cycle, that's why FPGA needs external configuration chip. You can generate ROM, place it in configuration memory and it will be uploaded to the FPGA every power cycle.

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    Yes. Unfortunately in this case ROM only means what it means, i.e. read-only memory. It doesn't mean that it is persistent. A M9K block in ROM mode is simply a RAM block whose write function is disabled.

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    It sounds like what you want is non-volatile RAM, not ROM. ROM content never changes, but it sounds like you want to save data even when power is off. Is that right? If so, you need to use some form of external EEPROM.