Serial Port Complete - Latest Microcontroller projects

Chapter 11

This code sets up an ISR to respond to received serial-port data:

// Interrupt vector for high-priority interrupts.

#pragma code high_vector = 0x8

void interrupt_at_high_vector (void)

{

// Define the function to execute on an interrupt.

_asm goto high_isr _endasm

}

// The ISR function.

#pragma interrupt high_isr

void high_isr(void)

{

if ((PIR1bits.RCIF == 1) && (PIE1bits.RCIE == 1)

{

// The serial port has received a byte.

// Place code to read and respond to received data here.

// Reset the ISR flag.

PIR1bits.RCIF = 0;

}

// Check the interrupt flags for any other enabled interrupts.

}

. 
 
 

Microcontrollers typically require firmware support for hardware flow control.

When the firmware has data to send, a hardware interrupt or firmware polling

can detect when the flow-control input is in the required state. When receiving

data, firmware can set the flow-control output as needed to prevent overruns.

To use hardware flow control on a hardware serial port, select any two otherwise

unused port bits and configure one bit as an input and the other as an output.