General-purpose timer (TIMx) RM0008
308/690
Figure 139. Triggering timer 2 with Enable of timer 1
Using one timer as prescaler for another timer
For example, you can configure Timer 1 to act as a prescaler for Timer 2. Refer to
Figure 135 for connections. To do this:
● Configure Timer 1 master mode to send its Update Event (UEV) as trigger output
(MMS=010 in the TIM1_CR2 register). then it outputs a periodic signal on each counter
overflow.
● 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 external clock mode 1 (SMS=111 in TIM2_SMCR register).
● Start Timer 2 by writing ‘1’ in the CEN bit (TIM2_CR1 register).
● Start Timer 1 by writing ‘1’ in the CEN bit (TIM1_CR1 register).
Starting 2 timers synchronously in response to an external trigger
In this example, we set the enable of timer 1 when its TI1 input rises, and the enable of
Timer 2 with the enable of Timer 1. Refer to Figure 135 for connections. To ensure the
counters are aligned, Timer 1 must be configured in Master/Slave mode (slave with respect
to TI1, master with respect to Timer 2):
● Configure Timer 1 master mode to send its Enable as trigger output (MMS=001 in the
TIM1_CR2 register).
● Configure Timer 1 slave mode to get the input trigger from TI1 (TS=100 in the
TIM1_SMCR register).
● Configure Timer 1 in trigger mode (SMS=110 in the TIM1_SMCR register).
● Configure the Timer 1 in Master/Slave mode by writing MSM=’1’ (TIM1_SMCR
register).
● 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 the TIM2_SMCR register).
TIMER 2-TIF
Write TIF=0
75 00 01
CK_INT
TIMER1-CEN=CNT_EN
TIMER1-CNT
TIMER2-CNT
02
TIMER1-CNT_INIT
CD 00 E7 E8 EA
TIMER2-CNT_INIT
TIMER2
write CNT
E9
To Next Page
Loading...
Need help?
General
