PIC18F23K22-ESLASHML datasheet(186/496 Pages) MICROCHIP

186 / 496 page

PIC18(L)F2X/4XK22

DS41412C-page 186

Preliminary

 2010 Microchip Technology Inc.

14.3.6

PWM RESOLUTION

The resolution determines the number of available duty

cycles for a given period. For example, a 10-bit resolution

will result in 1024 discrete duty cycles, whereas an 8-bit

resolution will result in 256 discrete duty cycles.

The maximum PWM resolution is 10 bits when PRx is

255. The resolution is a function of the PRx register

value as shown by Equation 14-4.

EQUATION 14-4:

PWM RESOLUTION

14.3.7

OPERATION IN SLEEP MODE

In Sleep mode, the TMRx register will not increment

and the state of the module will not change. If the CCPx

pin is driving a value, it will continue to drive that value.

When the device wakes up, TMRx will continue from its

previous state.

14.3.8

CHANGES IN SYSTEM CLOCK

FREQUENCY

The PWM frequency is derived from the system clock

frequency. Any changes in the system clock frequency

will result in changes to the PWM frequency. See

Section 2.0 “Oscillator Module (With Fail-Safe

Clock Monitor)” for additional details.

14.3.9

EFFECTS OF RESET

Any Reset will force all ports to Input mode and the

CCP registers to their Reset states.

Note:

If the pulse width value is greater than the

period the assigned PWM pin(s) will

remain unchanged.

Resolution

4PRx





log



log

------------------------------------------ bits

TABLE 14-7:

EXAMPLE PWM FREQUENCIES AND RESOLUTIONS (FOSC = 32 MHz)

PWM Frequency

1.95 kHz

7.81 kHz

31.25 kHz

125 kHz

250 kHz

333.3 kHz

Timer Prescale (1, 4, 16)

PRx Value

0xFF

0x3F

0x1F

0x17

Maximum Resolution (bits)

6.6

TABLE 14-8:

EXAMPLE PWM FREQUENCIES AND RESOLUTIONS (FOSC = 20 MHz)

PWM Frequency

1.22 kHz

4.88 kHz

19.53 kHz

78.12 kHz

156.3 kHz

208.3 kHz

Timer Prescale (1, 4, 16)

PRx Value

0xFF

0x3F

0x1F

0x17

Maximum Resolution (bits)

6.6

TABLE 14-9:

EXAMPLE PWM FREQUENCIES AND RESOLUTIONS (FOSC = 8 MHz)

PWM Frequency

1.22 kHz

4.90 kHz

19.61 kHz

76.92 kHz

153.85 kHz

200.0 kHz

Timer Prescale (1, 4, 16)

PRx Value

0x65

0x19

0x0C

0x09

Maximum Resolution (bits)

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