# Ctrl-C¶

To interrupt a running system at any time and reset it to the prompt a keyboard command ctrl-c is often used. AmForth can honour such a keystroke as well. To achieve it, a small code change needs to be applied and a new hex file pair has to be flashed to the controller.

The code change affects the interrupt usart handler (drivers/usart-rx-isr.asm). Here add the 4 lines 5-8:

 1 2 3 4 5 6 7 8 9  lds xh, USART_DATA ; optional: check for certain character(s) (e.g. CTRL-C) ; and trigger a soft interrupt instead of storing the ; charater into the input queue. cpi xh, 3 brne usart_rx_store jmp 0 usart_rx_store: lds xl, usart_rx_in 

With this change, whenever the keyboard sends the ascii code 3 (for ctrl-c) it is catched immediately and a soft reset is made. it requires that the WANT_ISR_RX option is set to 1.