ORG 0013h ISR: push PSW PUSH ACC CJNE R0,#06h,ISR_X1 ISR_X1: jnc ISR_Exit ;buffer full - accept no more DTMF codes inc R0 mov A,P3 cjne A,#0101,ISR_X2 ;the DTMF value for 0 - I doubt it is, but Ro said so... clr A ISR_X2: mov @R0,A ISR_Exit: pop acc pop psw reti