# Game and Watch Test RAM Firmware

This is a minimal program designed to read the contents of the Flash chip in a Nintendo Game and Watch.

It uses software-driven SPI, which is much slower than using the OCTOSPI peripheral. But I haven't been able to read out the Flash memory in OCTOSPI memory-mapped mode yet. I'm probably forgetting a flag somewhere, but it's also possible that that internal memory region is protected by the chip's readout protection.

The SPI Flash data is printed out in a stream of hex digits over the ARM Cortex-M "semihosting" print output. It seems to work, but I haven't tried to analyze or verify the output yet. It'll take a few minutes to run, because there are 1024 * 1024 * 2 = 2097152 hex digits to print.

When I run this, the program usually crashes approximately 1/8 of the way through, printing:

stm32h7x.cpu0 -- clearing lockup after double fault

Presumably this is caused by the same sort of artefact of the stock firmware that causes the SPI Flash chip to reject commands after a hard reset. Or maybe it's because I leave the battery unplugged and the chip browns out after a period of high activity from the power that the USB cable can supply. I'm not sure, but you can run it 8 times with different starting addresses if that happens to you.

This repository **DOES NOT** contain the actual contents of the Flash chip. It's definitely okay to back up this sort of data for your own use (in the US), but I feel like it might not be okay to publish it on GitHub.