Hello,
I have a reference NIOS project in which the reset vector memory is selected as an external flash. I opened platform designer and found the following information. Picture attached below.
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There is not specific reason why it is greyed out. It is according to the base address you set in Platform Designer. You have the flash address set to 0x10000000, and the offset to 0x08b00000. Therefore, flash will start access at 0x18b00000.
I would like to reopen this thread with further question on reset vector for Nios.
Q1) You have mentioned Nios access the flash starting at " 0x18b0_0000". Does this 0x18b0_0000 represent an address present in Flash?.
Here is the picture of the platform designer for my system.
Here is a picture from the board test gui that has come along with the development kit. The gui mentions that the flash address is only between 0x0000_0000 to 0x0FFF_FF80.
And the QSF of this project shows only 26 address lines for the flash. so what is the actual memory of the flash we are talking about here?
note that the project can compile fine, and the nios can boot up, and TCP is up and running.
Q2) what does the reset vector address actually signify?. Does pointing the reset address vector to 0x18b0_0000 and choosing the reset vector memory as "ext_flash.uas" change/write something to the flash?. what does this address location denote?.
Note that we just pointed out this reset vector location to the non volatile memory, but then we only generate SOF, and program into the FPGA. never generated any pof or flash specific file. So, it makes me wonder what this reset vector actually signifies, and how come it works even if we point the reset vector memory to flash, despite not programming anything to flash!.
p.s: please feel free to write back with more questions incase if my statements or questions are not clear. I am happy to explain.
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