STM32L4R9I-EVAL with Memory-Mapped NOR Flash

[Octo]

Hello!

I am trying to use the NOR flash module on the STM32L4R9I-EVAl board. I've been able to use the ST-provided example without issue, but in trying to build a project through CubeIDE, I've run into an intermittent fault. Sporadically, my writes to the the flash module are interrupted, and I could use some help in determining why. In addition to memory-mapping the NOR flash on the board, I'm using the board as a USB mass storage device. In effect, I'm trying to turn the STM32L4R9I-EVAL board into a glorified flash drive using the NOR flash.

This first image shows a page write operation just after 237.27ms. The bytes clocked in are 0b00010010 and 0b11101101, or 0x12ED, the "page program" command from p.20 of the attached datasheet. After 2 ms, the sequence begins with 0xEC13, the "read" command from p.20 of the attached datasheet. Please note the behavior of the chip select pin, and that the page read ~2ms later shows that the flash chip has the value 255 at a series of addresses because of the preceding erase sequence.

This image shows a successful read and write. Please note how much more data is present in the read after 65ms.

I've attached some sample captures and notes in a .zip file, as well as my project, and the datasheet for the flash module (it's a .pdf, if you like to be warned about those). Please don't hesitate to ask for clarification, and thank you for your consideration!