Datasheet

PICkit™ 3 Debug Express Lessons

FIGURE 3-44: LESSON 8 INTERRUPT SFRS

In the Lesson 8 source code, all the statements to change the rotation direction are in

the INT0 switch interrupt function, and the statements to rotate the LED display are in

the TMR0 interrupt function. All that remains in the main program is a while() loop

that updates the PORTD register with LED_Display. This statement could have also

been placed in the TMR0 interrupt function, but is left in the main program to illustrate

how the main program runs continuously and interacts with the interrupts.

Single Priority Interrupts

If only a single level of interrupts were used (RCON bit IPEN = 0), then it is only

necessary to define the interrupt vector at 0x0008, and a single Interrupt Service

Routine function with #pragma interrupt. All priority bit settings are ignored. The

function of the INTCON bits GIEH and GIEL become GIE and PEIE, respectively, with

the following functions:

3.8.3 Build and Run the Lesson 8 Code with PICkit 3 Debug Express

Build and program the Lesson 8 project, then Run the application in the debugger.

Turning the demo board potentiometer will affect the rotation speed of the LEDs. The

switch may be pressed to reverse the rotation. Use breakpoints to explore the

interrupting functions.

INTCONbits.GIE INTCONbits.PEIE Interrupt Functions

00No Interrupts; all interrupts disabled.

01No Interrupts; all interrupts disabled.

10Only interrupts enabled in INTCONx

enabled.

All PIEx interrupts remain disabled.

11All interrupts, including those enabled in

PIEx registers, are enabled.