Introduction to Microcontrollers Lab Manual - Microchip

LABS
To use the Stopwatch, insert two breakpoints around the section of code you wish to
time. Run the code to the first breakpoint, “Zero” the StopWatch and then run the code
to the next breakpoint. The Stopwatch will show the number of instruction cycles and
time between the two breakpoints.
Hint: When using the Stopwatch with MPLAB SIM Simulator, it is important to set the
Simulator Processor Frequency correctly. Otherwise the Stopwatch time will be incorrect.
An easy way to test if this has been set properly is to set breakpoints around a
simple instruction such as MOV. This should execute in 0.062500 uSecs.
1.2.5 The Lab
1.2.5.1 OBJECTIVE
Program the PIC24 microcontroller to use a hardware timer to blink an LED at a 1 second
interval (LED on for 1 second then off for 1 second). Show your calculations for the
Timer delay.
Use a subroutine CALL or RCALL somewhere in the code. A common use would be to
move the configuration instructions for the timer into a subroutine. This keeps the main
line code cleaner with only one line required to initialize the timer module at the start of
the code.
Use the stopwatch to check your timer and verify it is actually running at 1 sec (5 sec
for the bonus).
Hint: Use one breakpoint at your LED toggle instruction (BTG PORTC, #2), run the
code to that breakpoint, then “Zero” the stopwatch and run it again.
1.2.5.2 BONUS
Modify the code and setup a 32-bit TIMER to blink the LED at a 5 sec interval. Show
your calculations for the timer delay.
1.2.5.3 PERTINENT INFORMATION
The basic program flow is illustrated in Figure 1-3.
DS51963A-page 16 2011 Microchip Technology Inc.