If shows errors also in reading internal ram, it means there is something bad with the SWD connection between onboard stlink and nucleo mcu. stm32-nucleo-f401re-w5500-usr-es1 - A try to get work W5500 chip (on USR-ES1) on STM32 Nucleo F401RE. "memory display" is set by default to 0x08000000 (flash), set it to 0x20000000 (internal ram) and size whatever small (like 0x200), does it show memory (it should even if locks are enable in option bytes) or does it still report error? What error? If it shoes data, it means stlink SWD is ok, just messed up with the option bytes. The Arduino connectivity support and ST Morpho headers make it easy to expand the functionality of the STM32 Nucleo open development platform with a wide choice of specialized shields. RustNucleo-F401RE (PCubuntu) STM32 Nucleo Board STM32F401. ST NUCLEO-F401RE Microcontrollers: Frequently-viewed manuals. it tells "can't read memory, disable readout protecion" upon device connect to stlink utility. The NUCLEO-F401RE is a STM32 Nucleo development board with STM32F401RET6 MCU allows user to build their own prototypes for embedded applications. If you see all the above but unknown flash size, it probbly means you have enabled some locking in option bytes (flash size, if i'm not wrong, is stored somewhare is OTP flash or bootrom, don't remember exactly). Photo of the experimental setup consisting of the ST Nucleo-401RE.
![12kb on nucleo f401re 12kb on nucleo f401re](https://i.ytimg.com/vi/DqhU1ep6Fcc/maxresdefault.jpg)
![12kb on nucleo f401re 12kb on nucleo f401re](https://www.etteam.com/prod2014/NUCLEO-F401RE/NUCLEO-F401RE_3re.jpg)
does the target cpu gets recognized (top right window)? Do you see Device, dev id, rev id, and flash size (unknown flash size or 512k)? If you see device and dev id, SWD between stlink and mcu is at least working. operate within 12 KB of SRAM without impacting speed. Microcontrolador de alto desempeo ARM Cortex-M4, 84 MHz, 32 bits, FPU, 512 kB flash, 96 kB SRAM, hasta 50 pines I/O, ADC de 12 bits 2.4 Msps 10 ch, 10 timers, 3x I2C, 3x USARTs, 4x SPIs, SDIO, USB 2.0, conectores estndar Arduino UNO R3 y ST Morpho para conexin y expansin, habilitado para mbed, soporta IDE's de IAR. Just to restrict the possible issue, i would suggest to open stlink utility and: stm32 nucleo(64) nucleo-f103rbnucleo-f302r8nucleo-f303renucleo-f401renucleo-f410rb STM32CubeF3V1.11.