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General-purpose timer modes

AN4013

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DocID022500 Rev 4

2.6

Timer one pulse mode

One pulse mode (OPM) is a particular case of the input capture mode and the output

compare mode. It allows the counter to be started in response to a stimulus and to generate

a pulse with a programmable length after a programmable delay.

To configure the timer this mode:

Configure the input pin and mode:

Select the TIxFPx trigger to be used by writing CCxS bits in CCMRx register.

Select the polarity of the input pin by writing CCxP and CCxNP bits in CCER

Configure the TIxFPx trigger for the slave mode trigger by writing TS bits in SMCR

Select the trigger mode for the slave mode by writing SMS = 110 in SMCR

Configure the output pin and mode:

Select the output polarity by writing CCyP bit in CCER register.

Select the output compare mode by writing OCyM bits in CCMRy register (PWM1

or PWM2 mode).

Set the delay value by writing in CCRy register.

Set the auto reload value to have the desired pulse: pulse = TIMy_ARR -

TIMy_CCRy.

Select the one pulse mode by setting the OPM bit in CR1 register, if only one pulse is to

be generated. Otherwise this bit should be reset.

Delay = CCRy/(TIMx_CLK/(PSC + 1))

Pulse-Length = (ARR - CCRy)/(TIMx_CLK/(PSC + 1))

For more details on using the timer in this mode, refer to the examples provided in the

STM32xx standard peripheral libraries, in the /Project/STM32xx_StdPeriph_Examples/

TIM/OnePulse folder.

2.7

Timer Asymmetric PWM mode available for

STM32F30x and STM32F3x8 lines

The asymmetric mode allows generating a center-aligned PWM signals with a

programmable phase shift. For a dedicated channel, the phase shift and the pulse length

are programmed using the two TIMx_CCRx register (TIMx_CCR1 and TIMx_CCR2 or

TIMx_CCR3 and TIMx_CCR4), the frequency is determined by the value of the TIMx_ARR

programming the OCxM bits in TIMx_CCMRx register:



OCxM = 1110 to use the Asymmetric PWM1, in this mode the output reference has

the same behavior as in PWM1 mode. When the counter is counting up the output

reference is identical to OC1/3REF, when the counter is down counting, the output

reference is identical to OC2/4REF



OCxM = 1111 to use the Asymmetric PWM2, in this mode the output reference has the

same behavior as in PWM2 mode. When the counter is counting up the output

reference is identical to OC1/3REF, when the counter is down counting, the output

reference is identical to OC2/4REF

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