EM357-RTR datasheet(131/241 Pages) SILABS

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131

Rev 1.3

Figure 9.22. Edge-Aligned PWM Waveforms (ARR = 8)

9.3.9.2. PWM Edge-Aligned Mode: Down-Counting Configuration

Down-counting is active when the TIM_DIR bit in the TIMx_CR1 register is high. Refer to "9.3.2.2. Down-Counting

Mode" on page 119 for more information.

In PWM mode 1, the reference signal OCyREF is low as long as TIMx_CNT > TIMx_CCRy, otherwise it becomes

high. If the compare value in TIMx_CCRy is greater than the auto-reload value in TIMx_ARR, then OCyREF is held

at 1. Zero-percent PWM is not possible in this mode.

9.3.9.3. PWM Center-Aligned Mode

Center-aligned mode is active except when the TIM_CMS bits in the TIMx_CR1 register are 00 (all configurations

where TIM_CMS is non-zero have the same effect on the OCyREF/OCy signals). The compare flag is set when the

counter counts up, when it counts down, or when it counts up and down, depending on the TIM_CMS bits

configuration. The direction bit (TIM_DIR) in the TIMx_CR1 register is updated by hardware and must not be

changed by software. Refer to the "9.3.2.3. Center-Aligned Mode (Up/Down Counting)" on page 120 for more

information.

Figure 9.23 shows some center-aligned PWM waveforms in an example where:



TIMx_ARR = 8



PWM mode is the PWM mode 1



The output compare flag is set when the counter counts down corresponding to the center-aligned mode 1

selected for TIM_CMS = 01 in the TIMx_CR1 register

EM357-RTR 数据表(PDF) 131 Page - Silicon Laboratories