Espressif ESP32 Technical Reference Manual page 427

16 Motor Control PWM (PWM)
Please note that in the Count-Up-Down Mode, when the counting direction is increasing, the timer range is [0,
period value - 1], and when the counting direction is decreasing, the timer range is [period value, 1]. That
is, in this mode, when synchronizing the timer to 0, decreasing counting direction will be illegal, namely,
MCPWM_TIMERn_PHASE_DIRECTION cannot be set to 1. Similarly, when synchronizing the timer to period
value, increasing counting direction will be illegal, namely, MCPWM_TIMERn_PHASE_DIRECTION cannot be
set to 0. Therefore, when the timer is synchronized to 0, the counting direction can only be increasing, and
MCPWM_TIMERn_PHASE_DIRECTION will be 0. When the timer is synchronized to the period value, the count-
ing direction can only be decreasing, and MCPWM_TIMERn_PHASE_DIRECTION will be 1.
Espressif Systems 427 ESP32 TRM (Version 5.2)
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