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

Altera_Forum
Honored Contributor II
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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
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Altera_Forum
Honored Contributor II
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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.

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Altera_Forum
Honored Contributor II
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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.

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Altera_Forum
Honored Contributor II
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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.

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