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Demonstration Program Operation

DS51584B-page 27

3.4

DEMONSTRATION CODE OPERATION

The following sections describe in more detail how the demonstration programs

interact with and take advantage of key dsPIC DSC, DSP and peripheral features. Full

details on the peripheral functionality and associated tasks are presented later in this

document.

3.4.1

Interrupt Processing

The demonstration code samples switches S1 and S2 and uses their status to operate

the LEDs associated with processor ports RD4 and RD5, respectively. If S1 is pressed,

it sets program flag “LED1on”. If S1 is pressed again, it resets program flag LED1on.

Similarly, if S2 is pressed, it toggles program flag LED2on.

Another interrupt routine checks flags LED1on and LED2on every 500 milliseconds. If

the LED1on is true, the LED labeled RD4 is toggled on and off every 0.5 seconds,

causing the LED to blink. If LED1on is not true, the LED remains off.

This demo program is illustrated in Figure 3-1.

FIGURE 3-1:

INTERRUPT PROCESSING FLOW DIAGRAM

START

INIT TIMER 1

LED1on = LED1on

S1 Pressed?

S2 Pressed?

LED2on = LED2on

S1 Released?

S2 Released?

Yes

Start of 0.5 sec

Timer1 Init

LED1on Flag Set?

RD4 = RD4

Turn RD4 Off

LED2on Flag Set?

RD5 = RD5

Turn RD5 Off

Return

Yes

For 0.5 Sec Interval

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