Timers and PWM

Question 1

What 8 aspects of the timer peripheral can be set up using registers

Answer 1

1. Which signal source it counts
2. When it starts and stops running
3. Whether it counts rising or falling edges
4. Which direction it counts
5. What happens when it overflows
6. If and how it is reloaded
7. Whether its value is captured by another register
8. Whether it generates a signal or interrupt

Question 2

What is a watchdog timer and how does it work?

Answer 2

A hardware peripheral used to reset out-of-control programs.
It counts elapsed time. If it is not serviced (signaled) by the program before a defined time then it resets the CPU.

Question 3

Define PWM

Answer 3

A method of encoding information onto a single digital signal based on duty cycle.
Some devices can be driven by a PWM signal such as a motor or LED.

Question 4

SysTick Timer.
Does the SysTick Timer count up or down?

Answer 4

Down

Question 5

SysTick Timer.
What register does the timer store its current value in?

Answer 5

VAL or SYST_CVR
(Current value register)

Question 6

SysTick Timer.
What register does the timer load/relaod from?

Answer 6

LOAD or SYST_RVR
(Reload Value Register)

Question 7

SysTick Timer.
What register is used to display the timers status aswell as change its behaviour?

Answer 7

CTRL or SYST_CSR
(Control Status Register)

Question 8

SysTick Timer.
How is the timer frequency determined?

Answer 8

input frequency/LOAD+1