TM4C123 Input capture maximum count value 2^24 or 2^32?

Edriano De Araujo

Hello

I am measuring time using wide timer.

but i am having problem understanding how deep is the timer 2^24 or 2^32?

	SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOC);
	GPIOPinTypeTimer(GPIO_PORTC_BASE, GPIO_PIN_4);
	GPIOPinConfigure(GPIO_PC4_WT0CCP0);

	SysCtlPeripheralEnable(SYSCTL_PERIPH_WTIMER0);
        TimerConfigure(WTIMER0_BASE, TIMER_CFG_SPLIT_PAIR | TIMER_CFG_A_CAP_TIME_UP);
	TimerControlEvent(WTIMER0_BASE, TIMER_A, TIMER_EVENT_POS_EDGE);
	TimerIntEnable(WTIMER0_BASE, TIMER_CAPA_EVENT);
	TimerIntClear(WTIMER0_BASE, TIMER_CAPA_EVENT);
	IntEnable(INT_WTIMER0A);
	TimerEnable(WTIMER0_BASE, TIMER_A);

In this case the maximum counter value will be 2^32? when i get the value at the interrupt service?

TimerIntClear(WTIMER0_BASE, TIMER_CAPA_EVENT);
period_value = TimerValueGet(WTIMER0_BASE, TIMER_A);

thanks in advance.

over 10 years ago

0 Amit Ashara over 10 years ago

TI__Guru**** 244440 points

Hello Edriano

The Wide Timer in Split mode are 48 bit if prescalar is be used. The example code you have shown in the forum post, will generate an interrupt when the Pin sees a rising edge. So if the rising edge happens once in a year, then interrupt shall be fired once a year. If it is happening 10 times a second, then the interrupt shall be fired 10 times a second.

Regards
Amit

0 Edriano De Araujo over 10 years ago in reply to Amit Ashara

Intellectual 510 points

Hello Ammit.
thanks for your answer.
Yeas i know i am using to measure frequency so i have to measure interval between pulses.

I am really knew to TIVA series and in another micro i am used to the timer counts until 0xffffffff 32 bits. this way the math to solve actual time minus previews time is easier to achieve when an overflows happens. altthoug it will tak a lot of time to happen.

0 Edriano De Araujo over 10 years ago in reply to Amit Ashara

Intellectual 510 points

Ammit.

TimerConfigure(WTIMER0_BASE, TIMER_CFG_SPLIT_PAIR | TIMER_CFG_A_CAP_TIME_UP);

when i configure TIMER_CFG_SPLIT_PAIR doesn't it mean one timer why is it 48 bits?

0 Amit Ashara over 10 years ago in reply to Edriano De Araujo

TI__Guru**** 244440 points

Hello Edriano,

Make sure that you load the TAILR register with 0xFFFFFFFF to ensure that the timeout occurs when it reaches 0xFFFFFFFF and then starts from 0 as well,

Regards
Amit

0 Amit Ashara over 10 years ago in reply to Edriano De Araujo

TI__Guru**** 244440 points

Hello Edriano,

You are using a Wide Timer which is a 64 bit timer. When in split mode it becomes 32 bit timer. In Split mode a prescalar can be added which gives it another 16 bit making it 48 bits. if you do not program the prescalar then it will work as 32 bit timer.

Regards
Amit

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TM4C123 Input capture maximum count value 2^24 or 2^32?