Timer Diagram; Programming The Timer - Texas Instruments OMAP5910 Technical Reference Manual

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Figure 6–3. Timer Diagram

If LOAD_TIM = 0 and AR (auto-reload mode) = 1, the timer is always 0 and can

never decrement. Here the timer interrupt is asserted and stays asserted all

the time. Since the timer interrupts are edge-senditive, only one interrupt is

recognized because there is one initial edge, and then the interrupt is asserted

Before a timer can be used, you must enable its internal clock by setting the

CLOCK_ENABLE bit of the control timer register (CNTL_TIMER) to 1. A timer

is started by setting the ST field of the control timer register (CNTL_TIMER)

to 1. It is stopped by resetting this bit to 0. When the timer is stopped, the

content of the decrementer is frozen.

If the autoreload bit is disabled (AR field of control timer register (CNTL_TIM-

ER) is 0), the timer decrements from the loaded value down to zero and then

stops. If the autoreload bit is enabled (AR=1), the timer continues. A new value

(from the load register) is loaded into the timer when it passes though zero or

when it starts. An interrupt is produced when the corresponding timer passes

through zero.

To avoid undefined results, do not change the settings of the PTV or AR fields

of the control timer register (CNTL_TIMER) or the LOAD_TIM register while the

timer is running.

The timer value is held in the VALUE_TIM field of the READ_TIM and can be

read while the timer is running or stopped.

MPU Private Peripherals

Timer Description