EM6812F2TP24B datasheet(57/81 Pages) EMMICRO

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13.2.4 Stopping the timer

The timer stops always at the next clock following a valid stop condition. These are:

•

Reaching hex 00 in Zero-Stop mode.

•

In software start control if SWStart is cleared.

•

In external start control, on input state if the selected input value becomes 0.

•

In external start control, on input pulse, the timer stops at the 2

nd pulse.

Refer also to previous timing diagrams and hints for restart.

13.2.5 Clock selection

There are 8 different clock sources for each timer. Some of them come from external sources. The others are from the

prescaler1 or prescaler2. The selection is done with ClkXSel[2:0] in RegTimXCfg.

Table 49. Input clock selection

Timer1

Timer2

Timer3

Timer4

ClkXSel[2:0]

value

Selection with

Clk1Sel[2:0]

Selection

with

Clk2Sel[2:0]

Selection

with

Clk3Sel[2:0]

Selection

with

Clk4Sel[2:0]

000

PA0

PA1

PA2

PA3

001

PA4

PA5

PA6

PA7

010

Pr2CkSource

Pr2ClkSource

011

Pr2Ck[8]

Pr1CkSource

Pr2Ck[8]

Pr1ClkSource

100

Pr2Ck[6]

Pr1Ck[14]

Pr2Ck[4]

Pr1Ck[13]

101

Pr1CkSource

Pr1Ck[12]

Pr1CkSource

Pr1Ck[11]

110

Pr1Ck[13]

Pr1Ck[10]

Pr1Ck[13]

Pr1Ck[9]

111

Pr1Ck[11]

Pr1Ck[8]

Pr1Ck[9]

Pr1Ck[7]

Clock selection should only be changed while the timer is stopped to avoid timer clock glitches, which may influence the

actual counter value.

13.2.6 PWM and Frequency generation

With the pulse width modulation function, is possible to generate signals of a defined frequency and duty cycle. These

signals can be output on the port B as frequencies or PWM. The function of the PWM is based on the comparison of the

actual timer value and a compare value. PWM = ‘0’ when the timer starts counting until it reaches the comparison value,

then PWM=’1’ until the end of the loop when the timer reaches the value 0. See figure below for more details.

The PWM function is enabled with bit EnPWMX in RegTimXCfg. This bit enables the comparator and also routes the PWM

signal to the port B. Compare match interrupt can be generated in PWM mode. The bit TimEqX allows to select between

timer compare match IRQ or timer zero detect IRQ (default value). Also refer to chapter 13.2.8 Interrupts.

Figure 34. PWM or Frequency generation in Auto-Reload mode.

ClkIn

SwStartX

TimXLoad

TimXComp

PWMX

TimXStatus

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