STM32F101xx, STM32F102xx, STM32F103xx, STM32F105xx and ...

General-purpose timer (TIMx)
RM0008
Figure 141. Gating timer 2 with Enable of timer 1
CK_INT
TIMER1-CEN=CNT_EN
TIMER1-CNT_INIT
TIMER1-CNT
75 00 01
02
TIMER2-CNT
AB 00 E7 E8 E9
TIMER2-CNT_INIT
TIMER2
write CNT
TIMER 2-TIF
Write TIF=0
Using one timer to start another timer
In this example, we set the enable of Timer 2 with the update event of Timer 1. Refer to
Figure 139 for connections. Timer 2 starts counting from its current value (which can be
non-zero) on the divided internal clock as soon as the update event is generated by Timer 1.
When Timer 2 receives the trigger signal its CEN bit is automatically set and the counter
counts until we write ‘0’ to the CEN bit in the TIM2_CR1 register. Both counter clock
frequencies are divided by 3 by the prescaler compared to CK_INT (f CK_CNT = f CK_INT /3).
● Configure Timer 1 master mode to send its Update Event (UEV) as trigger output
(MMS=010 in the TIM1_CR2 register).
● Configure the Timer 1 period (TIM1_ARR registers).
● Configure Timer 2 to get the input trigger from Timer 1 (TS=000 in the TIM2_SMCR
register).
● Configure Timer 2 in trigger mode (SMS=110 in TIM2_SMCR register).
●
Start Timer 1 by writing ‘1’ in the CEN bit (TIM1_CR1 register).
Figure 142. Triggering timer 2 with update of timer 1
CK_INT
TIMER1-UEV
TIMER1-CNT
FD FE FF 00 01
02
TIMER2-CNT
45 46 47 48
TIMER2-CEN=CNT_EN
TIMER 2-TIF
Write TIF=0
352/995 Doc ID 13902 Rev 9