EM357-RTR datasheet(139/241 Pages) SILABS

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Rev 1.3

9.3.14. Timer Synchronization

The two timers can be linked together internally for timer synchronization or chaining. A timer configured in master

mode can reset, start, stop or clock the counter of the other timer configured in slave mode.

Figure 9.31 presents an overview of the trigger selection and the master mode selection blocks.

9.3.14.1. Using One Timer as Prescaler for the Other Timer

For example, to configure Timer 1 to act as a prescaler for Timer 2:



Configure Timer 1 in master mode so that it outputs a periodic trigger signal on each UEV. Writing

TIM_MMS = 010 in the TIM1_CR2 register causes a rising edge to be output on TRGO each time a UEV is

generated.



To connect the TRGO output of Timer 1 to Timer 2, configure Timer 2 in slave mode using ITR0 as an

internal trigger. Write TIM_TS = 100 in the TIM2_SMCR register.



Put the slave mode controller in external clock mode 1: Write TIM_SMS = 111 in the TIM2_SMCR register.

This causes Timer 2 to be clocked by the rising edge of the periodic Timer 1 trigger signal, which

corresponds to the Timer 1 counter overflow.



Finally, enable both timers: Set their respective TIM_CEN bits in the TIMx_CR1 register.

Note:

If OCy is selected on Timer 1 as trigger output (TIM_MMS = 1xx), its rising edge is used to clock the counter of Timer 2.

Figure 9.31. Master/Slave Timer Example

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