General-purpose timers (TIM15/TIM16/TIM17) RM0440
1388/2126 RM0440 Rev 4
30.4.25 Timer synchronization (TIM15)
The TIMx timers are linked together internally for timer synchronization or chaining. Refer to
Section 29.4.23: Timer synchronization for details.
Note: The clock of the slave peripherals (timer, ADC, ...) receiving the tim_trgo signal must be
enabled prior to receive events from the master timer, and the clock frequency (prescaler)
must not be changed on-the-fly while triggers are received from the master timer.
30.4.26 Using timer output as trigger for other timers (TIM16/TIM17)
The timers with one channel only do not feature a master mode. However, the OC1 output
signal can be used to trigger some other timers (including timers described in other sections
of this document). Check the “TIMx internal trigger connection” table of any timer on the
device to identify which timers can be targeted as slave.
The OC1 signal pulse width must be programmed to be at least 2 clock cycles of the
destination timer, to make sure the slave timer will detect the trigger.
For instance, if the destination's timer CK_INT clock is 4 times slower than the source timer,
the OC1 pulse width must be 8 clock cycles.
30.4.27 DMA burst mode
The TIMx timers have the capability to generate multiple DMA requests on a single event.
The main purpose is to be able to re-program several timer registers multiple times without
software overhead, but it can also be used to read several registers in a row, at regular
intervals.
The DMA controller destination is unique and must point to the virtual register TIMx_DMAR.
On a given timer event, the timer launches a sequence of DMA requests (burst). Each write
into the TIMx_DMAR register is actually redirected to one of the timer registers.
The DBL[4:0] bits in the TIMx_DCR register set the DMA burst length. The timer recognizes
a burst transfer when a read or a write access is done to the TIMx_DMAR address), i.e. the
number of transfers (either in half-words or in bytes).
The DBA[4:0] bits in the TIMx_DCR registers define the DMA base address for DMA
transfers (when read/write access are done through the TIMx_DMAR address). DBA is
defined as an offset starting from the address of the TIMx_CR1 register.
Example:
00000: TIMx_CR1,
00001: TIMx_CR2,
00010: TIMx_SMCR,
For example, the timer DMA burst feature could be used to update the contents of the CCRx
registers (x = 2, 3, 4) on an update event, with the DMA transferring half words into the
CCRx registers.
This is done in the following steps:
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