System reset or download (Error 258) fails on XMC1000 and NXP LPC family devices, when the debugger uses the reset vector catch mechanism to stop the CPU after the CPU reset release.
Always leave the CORERESET exception unchecked.
1. Open Hardware | CPU Options | CORE0.
2. Make sure CORERESET is unchecked.
The debug system supports a protection mechanism that prevents debug access to the system address area when the time startup software (SSW) is running. Firmware controls the debug access, based on the register setting. Configuring reset vector catch (CORERESET) stops the execution of firmware and debug access is then not enabled, preventing the external debugger from getting control.