Hi, Is it possible to simulate a P16F87x USART receive interrupt (i.e. set the RCIF flag) using a Debug stimulus (Debug>Simulator Stimulus>....) under MPLAB for Windows ver. 4.0. If so, should asynchronous, clock or register stimulus be used when the following simple code is run? ORG 0X000 RESET_V GOTO START ORG 0X004 RX_INT_V GOTO $ START BCF STATUS,RP0 CLRF PORTC BSF STATUS, RP0 MOVLW B'11000000' MOVWF TRISC&0X07F MOVLW D'103' MOVWF SPBRG&0X07F MOVLW 0X40 MOVWF TXSTA&0X07F BSF PIE1&0X07F,TXIE BSF PIE1&0X07F,RCIE BSF INTCON,GIE BSF INTCON,PEIE BCF STATUS,RP0 MOVLW 0X90 MOVWF RCSTA GOTO $ END