CCS/MSP430FR5959: Timer In Capture mode.

I had this idea that there was a standard Example program that illustrates this, but I couldn't find it, so I spent a few minutes constructing one that runs on an FR5969 Launchpad.

You actually only need about 6 lines of this, but I packaged it as a demo (jumper P1.2 to P2.0) so you (and I) could be convinced that it worked.

No warranty, no support, and all that.

///
//  main.c
//  Demonstrate TB0CLK input. Patching P1.2 to P2.0 blinks an LED.
//
//  Disclaimer: No warranty, no support. I may not even exist.
//
#include <msp430.h>
#define HZ          1000000UL           // SMCLK ~1MHz after Reset
#define TRIGGER_HZ  50000UL             // 50 kHz out from TA1.1 into TB0CLK
#define TRIGGER_PERIOD (HZ/TRIGGER_HZ)  // TA1.1 output period 20 ticks
#define LED_HZ      1UL                 // 1Hz (two toggles) on the LED
#define LED_PERIOD  (TRIGGER_HZ/LED_HZ/2) // 25000 pulses per LED toggle

///
//  main()
//
int
main(void)
{
    WDTCTL = WDTPW | WDTHOLD;   // stop watchdog timer

    //  Launchpad P1.0 LED
    P1OUT &= ~BIT0;             // Initially off
    P1DIR |= BIT0;              // Output

    //  Here's the timer clock input part:
    //  Clock TB0 from TB0CLK (P2.0), inconveniently located on J13 (TXD).
    //  Pulses are counted in TB0R. An interrupt occurs after a given number
    //  of pulses (LED_PERIOD).
    P2DIR &= ~BIT0;             // P2.0 input
    P2SEL1 |= BIT0;             // P2.0 assigned TB0CLK
    P2SEL0 |= BIT0;             //  per SLAS704F Table 6-52
    TB0CCTL6 = CCIE;            // Interrupt after
    TB0CCR6 = LED_PERIOD;       //    25000 input pulses (1Hz blink)
    TB0CTL |= TBSSEL_0 | ID_0 | MC_2 | TBCLR; // TBCLK/1, Continuous [,Clear]

    //  Here's the demo part: Generate a 50% duty cycle at apx 50kHz on TA1.1.
    //  To see it, jumper P1.2 (TA1.1) to P2.0 (TB0CLK) so TB0 sees some clock pulses.
    P1SEL0 |= BIT2;             // P1.2 as TA1.1
    P1SEL1 &= ~BIT2;            //  per SLAS704F Table 6-49
    P1DIR |= BIT2;
    TA1CCR0 = TRIGGER_PERIOD-1; // Cycle 20 clocks (50kHz)
    TA1CCR1 = TRIGGER_PERIOD/2; // Halfway for 50% duty cycle
    TA1CCTL1 = OUTMOD_7;        // Reset/Set
    TA1CTL = TASSEL_2 |ID_0 | MC_1 | TACLR; // SMCLK/1, Up [,Clear]

    PM5CTL0 &= ~LOCKLPM5;       // Engage GPIOs
    __enable_interrupt();

    //  Not much to do now
    while (1)
    {
        LPM0;
    }
	/*NOTREACHED*/
	return 0;
}

///
//  ISR for TB0CCR6 (every LED_PERIOD pulses)
//
#pragma vector=TIMER0_B1_VECTOR
__interrupt void
timerB1_ISR(void)
{
    TB0CCTL6 &= ~CCIFG;         // Clear IFG
    TB0CCR6 += LED_PERIOD;      // Move forward for next time
    P1OUT ^= BIT0;              // Blink (well, half a blink anyway)
    return;
}