Memory operation failed

Could not read or write to the device memory.

READ_WRITE_FAILED

Symptoms

  • Individual variable reads fail while the connection itself stays up.
  • Errors appear when accessing a specific address or peripheral region.
  • Reads start failing after the firmware enters a low-power mode.

Likely causes

  • The address is invalid or unmapped for this MCU (stale symbol file from a different build/chip).
  • Accessing a peripheral register whose clock is gated triggers a bus fault on some devices.
  • The MCU entered STOP/STANDBY and its debug interface lost access to the bus.
  • A marginal SWD link corrupts transfers under load.

How to fix it

  1. Confirm the symbol file matches the firmware

    If the .elf loaded in MCUHex is from a different build than what is flashed, addresses point into the wrong places. Re-upload the .elf that matches the running firmware.

  2. Check the address region

    Verify the variable lives in RAM/flash mapped on this exact part (a smaller-memory variant of the same family maps less RAM).

  3. Keep debug alive in low-power modes

    On STM32, set the DBGMCU low-power debug bits (DBG_STOP/DBG_STANDBY) during development so SWD keeps working when firmware sleeps.

  4. Stabilize the link

    Shorten wiring and reduce noise if failures are random rather than address-specific.

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