Hi all, I am facing a problem while debugging the code. The following error is comming and it is jumping to disassembly Error message is *** 65: access voilation at 0X001B: no 'execute/read' permission This location is Timer 1 interrupt routine. My code is as follows Following is a part of total code. <pre void sendserial(char); void init_run(void); //void init_stop(void); //void send_response(void); void main(void) { P1 = 0x00 ; //Initialise P1.0 to P1.3 used as output & //Initialise P1.4 to P1.7 used as input SP = 0x50; SCON = 0x50; //Set Serial IO to receive.And select mode1 TMOD = 0x21; //configure timer for the correct baud rate TH0 = 0x00; TL0 = 0xF7; TH1 = 0xFD; //TH1: reload value for 9600baud @11.059MHz TL1 = 0xFD; //TH1: reload value for 9600baud @11.059MHz TCON = 0x00; //Set timer to not running T2CON= 0x00; T2MOD= 0x02; // TI = 0; //clear transmit interrupt flag // RI = 0; //clear receive interrupt flag // TR0 = 1; //start timer 0 TR1 = 1; //start timer to Receive TR2 = 0; IE = 0xFA; ET0 = 1; //enable timer 0 interrupt // ET1 = 1; EA = 1; //Enable global interrupt ES = 1; //Enable serial interrupt PS=1; DE=0; while(1) { if(run) { sendserial('R'); init_run(); } if(stop) { sendserial('S'); //init_stop(); } if(query) { sendserial('Q'); //send_response(); } } } void sendserial(char command) { int j; *(pos_ack+3) = command; sencnd = 0; sendchr = 7; for(j=0; j < 7; j++) { *(send_buf+j) = pos_ack[j]; DE = 1; TI = 0; } } void init_run(void) { run=0; TH2=0x13; TL2=0x88; Iref=0xff; Delay=5000; TR2=1; Stat=1; } /*void init_stop(void) { } void send_response(void) { } Thanks in advance.