STM8S datasheet(175/467 Pages) STMICROELECTRONICS

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RM0016

16-bit advanced control timer (TIM1)

261

Figure 70. Edge-aligned counting mode PWM mode 1 waveforms (ARR = 8)

Down-counting configuration

Down-counting is active when the DIR bit in the TIM1_CR1 register is high. Refer to Down-

counting mode on page 145

In PWM mode 1, the reference signal OCiREF is low as long as TIM1_CNT> TIM1_CCRi.

Otherwise, it becomes high. If the compare value in the TIM1_CCRi registers is greater than

the auto-reload value in the TIM1_ARR register, OCiREF is held at 1. Zero percent PWM is

not possible in this mode.

PWM center-aligned mode

Center-aligned mode is active when the CMS bits in the TIM1_CR1 register are different

from 00 (all the remaining configurations have the same effect on the OCiREF/OCi signals).

The compare flag is set when the counter counts up, down, or up and down depending on

the CMS bits configuration. The direction bit (DIR) in the TIM1_CR1 register is updated by

hardware and is read-only in this mode (refer to Center-aligned mode (up/down counting) on

page 147).

Figure 71 shows some center-aligned PWM waveforms in an example where:

•

TIM1_ARR = 8,

•

PWM mode is PWM mode 1

•

The flag is set (arrow symbol in Figure 71) in three different cases:

–

When the counter counts down (CMS = 01)

–

When the counter counts up (CMS = 10)

–

When the counter counts up and down (CMS = 11)

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