else
' Check other flags for enabled interrupts and take action as needed.
endif
RESUME
ENABLE
Ports for Embedded Systems
255
The OpenUSART function enables the receive interrupt by setting the second
parameter to USART_RX_INT_ON:
OpenUSART (USART_TX_INT_OFF &
USART_RX_INT_ON &
USART_ASYNCH_MODE &
USART_EIGHT_BIT &
USART_CONT_RX &
USART_BRGH_LOW,
77);
Another way to enable the serial-port receive interrupt is to set the bit directly:
PIE1bits.RCIE = 1;
If not using interrupt priority (IPEN = 0), set these bits:
// Disable using interrupt priority.
RCONbits.IPEN = 0;
// Enable all unmasked interrupts.
INTCONbits.GIE = 1;
// Enable all unmasked peripheral interrupts.
INTCONbits.PEIE = 1;
If using interrupt priority (IPEN = 1) and the serial interrupt is high priority,
set these bits:
// Enable using interrupt priority.
RCONbits.IPEN = 1;
// Configure the receive interrupt as high priority.
IPIR1bits.RCIP = 1;
// Enable all high-priority interrupts.
INTCONbits.GIEH = 1;
Chapter 11
256
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.
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