[Answered]: MMU and un-mapped flash entry numbers

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[Answered]: MMU and un-mapped flash entry numbers

Postby kolban » Sat Feb 24, 2018 11:52 pm

Using the language in the ESP32 technical reference relating to MMU ... for flash we have 256 entries where each entry corresponds to a 64K range of address space. We can map an entry to a corresponding 64K of flash storage. Each entry in the MMU table consists of:

8 bits of flash storage page identity
1 bit of MMU table entry defined/undefined 0 = defined, 1 = undefined.

With this background, here comes my question.

If I access an address in storage in the ESP32 that is governed by the MMU flash mapping and the corresponding entry for that region of memory is flagged as undefined (control bit is 1), what ... if anything ... does that mean? Will an exception be thrown? Is there some form of "implicit" mapping?
Last edited by kolban on Sun Feb 25, 2018 3:52 am, edited 1 time in total.
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Re: MMU and un-mapped flash entry numbers

Postby ESP_Sprite » Sun Feb 25, 2018 3:48 am

If I recall correctly, the flash cache will throw an interrupt, which in normal ESP-IDF invokes the panic handler.

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