Dear all, I have attempted to send a character through serial port 2 in the Dallas DS80C400. However, it seems that the interrupt service routine of serial port 2 does not occur. Could anyone check the following code and point me to the solution? (Note: SCON2 is not bit addressable) #include <REG400.H> /*special function register declarations*/ #include <stdio.h> /*prototype declarations for I/O functions */ void uart_init (void) { T3CM = 0x72; SCON2 = 0x50; TH3 = 0xFE; ES2 = 1; //enable interrupt serial port 2 PS2 = 1; //set priority to interrupt serial port 2 EA = 1; //enable global interrupt } void uart_interrupt (void) interrupt 4 { SCON2 = 0x50; //clear bit TI_2 SBUF2 = 'A'; //transmit 'A' to serial port 2 } void main(void) { uart_init (); SCON2 = 0x52; //set bit TI_2 while(1) { } }