Low-power timer (LPTIM) RM0444
840/1390 RM0444 Rev 5
Figure 275. Waveform generation
26.4.11 Register update
The LPTIM_ARR register and LPTIM_CMP register are updated immediately after the APB
bus write operation, or at the end of the current period if the timer is already started.
The PRELOAD bit controls how the LPTIM_ARR and the LPTIM_CMP registers are
updated:
• When the PRELOAD bit is reset to ‘0’, the LPTIM_ARR and the LPTIM_CMP registers
are immediately updated after any write access.
• When the PRELOAD bit is set to ‘1’, the LPTIM_ARR and the LPTIM_CMP registers
are updated at the end of the current period, if the timer has been already started.
The LPTIM APB interface and the LPTIM kernel logic use different clocks, so there is some
latency between the APB write and the moment when these values are available to the
counter comparator. Within this latency period, any additional write into these registers must
be avoided.
The ARROK flag and the CMPOK flag in the LPTIM_ISR register indicate when the write
operation is completed to respectively the LPTIM_ARR register and the LPTIM_CMP
register.
After a write to the LPTIM_ARR register or the LPTIM_CMP register, a new write operation
to the same register can only be performed when the previous write operation is completed.
Any successive write before respectively the ARROK flag or the CMPOK flag be set, will
lead to unpredictable results.
MS32467V2
LPTIM_ARR
Compare
0
PWM
One shot
Set once
PWM
One shot
Set once
Pol = 0
Pol = 1
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