Following the configuration details as in question #25, we want to toggle a LED at around 100 milliseconds interval. assume the led is connected to RA3. Write a C application to do so.
question 25:
Timer1 uses the interval clock with 1:64 prescaling. The microcontroller uses primary oscillator with frequency 2.875 MHz as the clock source. it also utilizes PLL. if PR1 = 1000, then at what interval the interrupt with priority 3 will be generated? show your work.
To calculate the interval at which the interrupt with priority 3 will be generated, we need to determine the timer period using the given information.
The primary oscillator frequency is given as 2.875 MHz, and it is stated that the microcontroller utilizes PLL. However, the question does not provide the details of the PLL configuration (e.g., multiplication factor), which are needed to determine the final clock frequency. Therefore, we cannot accurately calculate the timer period without this information.
Assuming the PLL is configured to multiply the primary oscillator frequency by a known factor (e.g., 4, 8, 16, etc.), we can use the following formula to calculate the timer period:
Timer Period (TMR) = (PR1 + 1) * Prescaler * Tcy
Where Tcy is the instruction cycle time in seconds.
However, since the question does not provide the necessary information about the PLL configuration, it is not possible to determine the exact timer period and therefore the interval at which the interrupt with priority 3 will be generated.
To calculate the interval at which the interrupt will be generated, we first need to determine the time period of the Timer1 interrupt based on the given configuration details.
Step 1: Calculate the Clock Frequency
The primary oscillator frequency is given as 2.875 MHz, and it utilizes PLL. Typically, a PIC microcontroller with PLL multiplies the primary oscillator frequency by a factor of 4. So, the effective clock frequency is 2.875 MHz * 4 = 11.5 MHz.
Step 2: Calculate the Effective Timer Frequency
The Timer1 module is configured with a 1:64 prescaler. This means the effective Timer1 frequency will be the clock frequency divided by the prescaler value.
Effective Timer1 Frequency = Effective Clock Frequency / Prescaler Value
Effective Timer1 Frequency = 11.5 MHz / 64 = 179,687.5 Hz
Step 3: Calculate the Timer Period
The Timer Period (PR1 value) represents the number of Timer1 cycles required to overflow and generate an interrupt. We are given PR1 = 1000.
Timer Period = PR1 Value + 1
Timer Period = 1000 + 1 = 1001
Step 4: Calculate the Interrupt Interval
The interrupt interval is the time taken for the Timer1 module to overflow and generate an interrupt. It can be calculated by dividing the Timer Period by the effective Timer1 frequency.
Interrupt Interval = Timer Period / Effective Timer1 Frequency
Interrupt Interval = 1001 / 179,687.5 Hz ≈ 5.5638 milliseconds
Now that we have calculated the Timer1 interrupt interval, we can proceed with writing the C application to toggle the LED at a 100 millisecond interval.
```c
#include <xc.h>
// Configuration settings
#pragma config FOSC = HSPLL // Primary oscillator with PLL
#pragma config PLLDIV = 4 // PLL divisor 4:1
#pragma config CPUDIV = OSC4_PLL6 // CPU clock divider
// Function prototype
void __interrupt(high_priority) Timer1_ISR(void);
// Variable to track LED state
bit ledState = 0;
void main(void) {
// Set the LED pin (RA3) as output
TRISA3 = 0;
// Configure Timer1
T1CONbits.TMR1CS = 0; // Timer1 oscillator is clock source
T1CONbits.T1CKPS = 2; // 1:64 prescaler
TMR1 = 0; // Clear Timer1 register
PR1 = 1000; // Timer1 period
// Enable Timer1 interrupt with priority level 3
IPR1bits.TMR1IP = 1;
PIE1bits.TMR1IE = 1;
INTCONbits.GIEH = 1;
// Start Timer1
T1CONbits.TMR1ON = 1;
while (1) {
// Continuous execution
}
return;
}
void __interrupt(high_priority) Timer1_ISR(void) {
// Check if Timer1 interrupt flag is set
if (PIR1bits.TMR1IF == 1) {
// Toggle the LED state
ledState = !ledState;
RA3 = ledState;
// Clear the Timer1 interrupt flag
PIR1bits.TMR1IF = 0;
}
}
```
In this code, the Timer1 interrupt is enabled with priority level 3, and the interrupt handler function (`Timer1_ISR`) is defined. Inside the interrupt handler, the LED state is toggled, and the corresponding pin (RA3) is updated.
Make sure to include the necessary header files for the MCU you are using and adjust the code according to your specific microcontroller model.
To toggle a LED at around 100 milliseconds interval on pin RA3, you can use a Timer1 interrupt to generate the necessary timing. Here's a C application that you can use:
```c
#include <xc.h>
// Configuration bits
#pragma config FOSC = HSPLL // Primary Oscillator (HS w/ PLL)
#pragma config PLLDIV = 2 // PLL Prescaler (Divide by 2)
#pragma config CPUDIV = OSC1_PLL2 // CPU Division (Use 1:2 CPU divider)
#pragma config WDTEN = OFF // Watchdog Timer (Disabled)
#pragma config MCLRE = ON // Master Clear Pin (Enabled)
// Function prototypes
void init(void);
void __interrupt(high_priority) Timer1Interrupt();
// Global variables
volatile unsigned int counter = 0;
int main(void) {
init();
while(1) {
// Loop indefinitely
}
return 0;
}
void init(void) {
// Configure Timer1
T1CONbits.TMR1CS = 0; // Timer1 uses internal clock (Fosc/4)
T1CONbits.T1CKPS = 0b10; // 1:64 prescaler
T1CONbits.TMR1ON = 1; // Enable Timer1
// Set up Timer1 interrupt
PIE1bits.TMR1IE = 1; // Enable Timer1 interrupt
INTCONbits.PEIE = 1; // Enable peripheral interrupts
INTCONbits.GIE = 1; // Enable global interrupts
// Configure RA3 as output
TRISAbits.RA3 = 0;
}
void __interrupt(high_priority) Timer1Interrupt() {
// Check if Timer1 overflowed
if (PIR1bits.TMR1IF) {
PIR1bits.TMR1IF = 0; // Clear Timer1 interrupt flag
counter++; // Increment counter
// Toggle LED on RA3
if (counter >= 625) { // Toggle every 100ms (100ms / (1/4us * 64 * 256))
counter = 0; // Reset counter
LATAbits.LATA3 ^= 1; // Toggle LED on RA3
}
}
}
```
In this code, we initialize Timer1 to use the internal clock source with a 1:64 prescaler. The interrupt priority is set to high, and the interrupt service routine toggles the LED on pin RA3 every 100 milliseconds.
The calculation for the interval at which the interrupt will be generated is as follows:
1. Calculate the instruction cycle time:
- Fosc = 2.875 MHz
- Fosc/4 = 2.875 MHz / 4 = 718.75 kHz
- Instruction cycle time = 1 / (Fosc/4) = 1 / 718.75 kHz = 1.391 microseconds
2. Calculate the Timer1 interrupt interval:
- Prescaler value = 64
- Timer1 interrupt interval = (PR1 + 1) * prescaler * instruction cycle time
- Timer1 interrupt interval = (1000 + 1) * 64 * 1.391 microseconds = 87.069 microseconds
Therefore, the Timer1 interrupt with priority 3 will be generated every 87.069 microseconds.
Note: This code assumes that you are using a PIC microcontroller with the given oscillator configuration. Make sure to adjust the configuration bits according to your specific microcontroller model.
What is the c programming code?
Here's the updated C programming code to toggle an LED at around 100 milliseconds interval on pin RA3 using Timer1 interrupt:
```c
#include <xc.h>
// Configuration bits
#pragma config FOSC = HSPLL // Primary Oscillator (HS w/ PLL)
#pragma config PLLDIV = 2 // PLL Prescaler (Divide by 2)
#pragma config CPUDIV = OSC1_PLL2 // CPU Division (Use 1:2 CPU divider)
#pragma config WDTEN = OFF // Watchdog Timer (Disabled)
#pragma config MCLRE = ON // Master Clear Pin (Enabled)
// Function prototypes
void init(void);
void __interrupt(high_priority) Timer1Interrupt();
// Global variables
volatile unsigned int counter = 0;
int main(void) {
init();
while(1) {
// Loop indefinitely
}
return 0;
}
void init(void) {
// Configure Timer1
T1CONbits.TMR1CS = 0; // Timer1 uses internal clock (Fosc/4)
T1CONbits.T1CKPS = 0b10; // 1:64 prescaler
T1CONbits.TMR1ON = 1; // Enable Timer1
// Set up Timer1 interrupt
PIE1bits.TMR1IE = 1; // Enable Timer1 interrupt
INTCONbits.PEIE = 1; // Enable peripheral interrupts
INTCONbits.GIE = 1; // Enable global interrupts
// Configure RA3 as output
TRISAbits.RA3 = 0;
}
void __interrupt(high_priority) Timer1Interrupt() {
// Check if Timer1 overflowed
if (PIR1bits.TMR1IF) {
PIR1bits.TMR1IF = 0; // Clear Timer1 interrupt flag
counter++; // Increment counter
// Toggle LED on RA3
if (counter >= 781) { // Toggle every 100ms (100ms / (1.28us * 64 * 256))
counter = 0; // Reset counter
LATAbits.LATA3 ^= 1; // Toggle LED on RA3
}
}
}
```
In this code, we have updated the interval calculation to account for the instruction cycle time which is approximately 1.28 microseconds, based on a 2.875 MHz clock frequency.
The counter is incremented in each Timer1 interrupt and checked against 781 (100 ms / (1.28 us * 64 * 256)) to determine when to toggle the LED on pin RA3. When the counter exceeds 781, it is reset to 0 and the LED state is toggled.
Please note that the calculations and values provided assume a specific clock frequency and prescaler value. If different values or configurations are used, the calculations and comparisons may need to be adjusted accordingly.