RM0312 datasheet(125/275 Pages) STMICROELECTRONICS

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RM0312

16-bit general purpose timer (TIM2/TIM3)

170

Figure 44. Gating Timer B with the counter enable signal of Timer A (CNT_EN)

Using one timer to start another timer

In this example, we set the enable of Timer B with the update event of Timer A. Refer to

Figure 42 for connections. Timer B 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 A.

When Timer B receives the trigger signal its CEN bit is automatically set and the counter

counts until we write ‘0’ to the CEN bit in the TIMx_CR1 register. Both counter clock

frequencies are divided by 4 by the prescaler compared to fMASTER (fCK_CNT = fMASTER/4).

Configure Timer A master mode to send its Update Event (UEV) as trigger output

(MMS=010 in the TIMx_CR2 register).

Configure the Timer A period (TIMx_ARR registers).

Configure Timer B to get the input trigger from Timer A (TS=001 in the TIMx_SMCR

Configure Timer B in trigger mode (SMS=110 in TIMx_SMCR register).

Start Timer A by writing ‘1’ in the CEN bit (TIMx_CR1 register).

Timer B-TIF

Write TIF=0

fMASTER

TIMERA-CEN = CNT_EN

TIMERA-CNT

TIMERB-CNT

TIMERA-UG

TIMERB-UG

TIMERB

write CNT

RM0312 Datenblatt(PDF) 125 Page - STMicroelectronics