UART to Bus

Force wrong prefix on the DUT serial input port let it be in unexpected state and can't respond to any valid command after that

Could you give some details? Or a short test bench to show the problem?

This is not a bug but the expected behavior. In text mode protocol you may reset the parser state machine by sending a new line / carriage return character. Simply pressing the enter key in a terminal will do the job. Binary mode is much less protected but sending 256 zeros and then sending a NOP command with ACK request should return the state machine to IDLE. The sequence of NOP with ACK may neet to be re-requested with a leading zero to solve the two possibilities of IDLE or MAIN_BIN_CMD states. Moti