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MSP430FR5969: Cannot Control PWM Duty Cycle When Module Block is CCR0

User 18793
Prodigy 40 points
Part Number: MSP430FR5969

Tool/software:

I want to output a PWM signal with a controlled duty cycle on P2.4.

I can control the duty cycle when the module block is any non-zero CCR. For example P1.2 using CCR1.

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P1DIR |= BIT2;
P1SEL0 |= BIT2;
P1SEL1 &= ~BIT2;
TA1CCR0 = 1000 - 1;
TA1CCTL1 = OUTMOD_7;
TA1CCR1 = 500;
TA1CTL = TASSEL_2 | MC_1;
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

It is obvious from the logic below that we cannot use the same workflow when the Module Block is 0 (Datasheet Table 6-14). CCR0 is being used to set both the duty cycle and period.

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P1DIR |= BIT7;
P1SEL0 |= BIT7;
P1SEL1 |= BIT7;
TA1CCR0 = 1000 - 1;
TA1CCTL0 = OUTMOD_7;
TA1CCR0 = 500;
TA1CTL = TASSEL_2 | MC_1;
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

I want to output a PWM signal with a controlled duty cycle on P2.4. Perhaps it is possible to use a different CCR for setting the period?

  • 0
    Guru 41995 points

    Can you describe what you mean by " want to output a PWM signal with a controlled duty cycle"

    Generally, the repetition rate is fixed and you adjust the pwm by adjusting the duty cycle.

  • 0 in reply to Keith Barkley
    Prodigy 40 points

    Generally, the repetition rate (period) is fixed and you adjust the pwm by adjusting the duty cycle.

    Yes, and you adjust the duty cycle using CCRx. If CCRx == CCR0, you lose the ability to adjust the duty cycle.

    I think I found confirmation that adjusting the duty cycle is not possible for PWM outputs based on CCR0. In SLAU367P Table 25-6, "Output mode. Modes 2, 3, 6, and 7 are not useful for TAxCCR0 because EQUx = EQU0".

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