RM0312 datasheet(124/275 Pages) STMICROELECTRONICS

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16-bit general purpose timer (TIM2/TIM3)

RM0312

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DocID022352 Rev 3

Figure 43. Gating Timer B with OC1REF of Timer A

In the example in Figure 43, the Timer B counter and prescaler are not initialized before

being started. So they start counting from their current value. It is possible to start from a

given value by resetting both timers before starting Timer A. You can then write any value

you want in the timer counters. The timers can easily be reset by software using the UG bit

in the TIMx_EGR registers.

In the next example, we synchronize Timer A and Timer B. Timer A is the master and starts

from 0. Timer B is the slave and starts from E7h. The prescaler ratio is the same for both

timers. Timer B stops when Timer A is disabled by writing ‘0’ to the CEN bit in the TIMx_CR1

Configure Timer A master mode to send its Output Compare 1 Reference (OC1REF)

signal as trigger output (MMS=100 in the TIMx_CR2 register).

Configure the Timer A OC1REF waveform (TIMx_CCMR1 register).

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

Configure Timer B in trigger gated mode (SMS=101 in TIMx_SMCR register).

Reset Timer A by writing ‘1’ in UG bit (TIMx_EGR register).

Reset Timer B by writing ‘1’ in UG bit (TIMx_EGR register).

Initialize Timer B to 0xE7 by writing ‘E7h’ in the Timer B counter (TIMx_CNTRL).

Enable Timer B by writing ‘1’ in the CEN bit (TIMx_CR1 register).

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

10. Stop Timer A by writing ‘0’ in the CEN bit (TIMx_CR1 register).

Timer B-TIF

Write TIF=0

3045

3047

3048

fMASTER

TIMER1-OC1REF

TIMER1-CNT

TIMER2-CNT

3046

RM0312 데이터시트(PDF) 124 Page - STMicroelectronics