Hi all!

For a project I am looking for a microcontroller that is capable of addressing memory mapped SRAM externally over (Q)SPI. I have seen many micro controllers that can attach external Flash memory, but these interfaces are read-only.

For context: I want to attach an FPGA to the micro controller and be able to access its register bus as a peripheral, plus the external 128MB of RAM that is attached to the FPGA, using a minimal number of pins and maximum memory space. I could easily implement a QSPI slave that bridges to the internal bus.

In an older version of this project, the FPGA contains a softcore, which effectively eliminates this problem. However, the CPU is relatively slow and all "standard" peripherals that you usually get in a microcontroller need to be implemented as well, such as UART, timers, USB, etc. In addition, when the Flash gets corrupted for whatever reason, thr FPGA won't boot, there is no CPU, and the device is bricked. An external micro would solve this, as it usually has a hard coded bootloader. For reference: the application is roughly 1MB, and the RAM used by the application directly is ~24MB, with an additional ~20MB used exclusively by the FPGA.

Any ideas? Also ideas in a different direction are very welcome.