I2CCON datasheet(89/210 Pages) MICROCHIP

89 / 210 page

DS70139G-page 89

dsPIC30F2011/2012/3012/3013

12.4.2

PWM PERIOD

The PWM period is specified by writing to the PRx

Equation 12-1.

EQUATION 12-1:

PWM frequency is defined as 1/[PWM period].

When the selected TMRx is equal to its respective

period register, PRx, the following four events occur on

the next increment cycle:

• TMRx is cleared.

• The OCx pin is set.

- Exception 1: If PWM duty cycle is 0x0000,

the OCx pin remains low.

- Exception 2: If duty cycle is greater than PRx,

the pin remains high.

• The PWM duty cycle is latched from OCxRS into

OCxR.

• The corresponding timer interrupt flag is set.

See Figure 12-2 for key PWM period comparisons.

Timer3 is referred to in Figure 12-2 for clarity.

FIGURE 12-2:

PWM OUTPUT TIMING

PWM period = [(PRx) + 1] • 4 • Tosc •

(TMRx prescale value)

Period

Duty Cycle

TMR3 = Duty Cycle

TMR3 = PR3

T3IF = 1

(Interrupt Flag)

OCxR = OCxRS

TMR3 = PR3

(Interrupt Flag)

OCxR = OCxRS

T3IF = 1

(OCxR)

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