Interrupts & Programming 8051 Hardware Interrupts

3. Programming Serial Interrupt
To use the serial interrupt the ES bit along with the EA bit is set. Whenever one byte of data is sent or received, the serial interrupt is generated and the TI or RI flag goes high. Here, the TI or RI flag needs to be cleared explicitly in the interrupt routine (written for the Serial Interrupt).
 
The programming of the Serial Interrupt involves the following steps:
1.        Enable the Serial Interrupt (configure the IE register).
2.        Configure SCON register.
3.        Write routine or function for the Serial Interrupt. The interrupt number is 4.
4.        Clear the RI or TI flag within the routine.
 
Example code
Send ‘A’ from serial port with the use of interrupt
// Sending ‘A’ through serial port with interrupt
// XTAL frequency 11.0592MHz 
void main()
{
	TMOD = 0x20;
	TH1 = -1;
	SCON = 0x50;
	TR1 = 1;
	IE = 0x90;
	while(1);
}
void ISR_sc(void) interrupt 4
{
	if(TI==1)
	{
		SBUF = ‘A’;
		TI = 0;
	}
	else
		RI = 0;
}
Example code
// Receive data from serial port through interrupt
// XTAL frequency 11.0592MHz 
void main()
{
	TMOD = 0x20;
	TH1 = -1;
	SCON = 0x50;
	TR1 = 1;
	IE = 0x90;
	while(1);
}
void ISR_sc(void) interrupt 4
{
	unsigned char val;
	if(TI==1)
	{
		TI = 0;
	}
	else
	{
		val = SBUF;
		RI = 0;
	}
}

 

Share   
  • 91129 reads