Does Unmatched have Pram, NVRAM, firmware or something similar (persistant RAM that do not erase with shutdown) ?
How to access\reset\update it ?


There’s a IS25WP256 SPI NOR flash chip on the board, connected through QSPI0. In Linux it appears as:

mtdblock0    31:0    0   32M  0 disk  

It’s not used by default (it came filled with 0xff here), but it can be used for boot. See Booting from Flash - #3 by drmpeg .


The only built-in firmware is the ZSBL (Zero-Stage BootLoader) in ROM 0x00001000-0x00001FFF and 0x00010000-0x00017FFF. It’s mask ROM so cannot be replaced. It loads the second stage from another device, either the flash or SD card.

persistant RAM that do not erase with shutdown

There’s also OTP, which is, as the name implies, one-time programmable. AFAIK by default it is only used for the serial number.

As for details how to access these, refer to the FU740-C000 manual.

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There is a gate ROM at address 0x1004 (reset vector) of the FU740-C000 and this gate ROM is non-volatile memory. The gate ROM reads MSEL switch input to determine if it loops reading MSEL or jumps to memory mapped QSPI0, memory mapped QSPI1, or ZSBL.

For more information on the gate ROM see: