PIC18LF45J10T-I/SP View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC18LF45J10T-I/SP

28/40/44-Pin High-Performance RISC Microcontrollers with nanoWatt Technology

Microchip Technology 

PIC18F45J10 FAMILY

14.4.2 PWM DUTY CYCLE

The PWM duty cycle is specified by writing to the

CCPR1L register and to the CCP1CON<5:4> bits. Up

to 10-bit resolution is available. The CCPR1L register

contains the eight MSbs and the CCP1CON<5:4>

contains the two LSbs. This 10-bit value is represented

by CCPR1L:CCP1CON<5:4>. The PWM duty cycle is

calculated by the following equation:

EQUATION 14-2:

PWM Duty Cycle = (CCPR1L:CCP1CON<5:4>) •

TOSC • (TMR2 Prescale Value)

CCPR1L and CCP1CON<5:4> can be written to at any

time, but the duty cycle value is not copied into

CCPR1H until a match between PR2 and TMR2 occurs

(i.e., the period is complete). In PWM mode, CCPR1H

is a read-only register.

The CCPR1H register and a 2-bit internal latch are

used to double-buffer the PWM duty cycle. This

double-buffering is essential for glitchless PWM opera-

tion. When the CCPR1H and 2-bit latch match TMR2,

concatenated with an internal 2-bit Q clock or two bits

of the TMR2 prescaler, the CCP1 pin is cleared. The

maximum PWM resolution (bits) for a given PWM

frequency is given by the following equation:

EQUATION 14-3:

( ) log FOSC

PWM Resolution (max) =

FPWM bits

log(2)

Note:

If the PWM duty cycle value is longer than

the PWM period, the CCP1 pin will not be

cleared.

14.4.3 PWM OUTPUT CONFIGURATIONS

The P1M1:P1M0 bits in the CCP1CON register allow

one of four configurations:

• Single Output

• Half-Bridge Output

• Full-Bridge Output, Forward mode

• Full-Bridge Output, Reverse mode

The Single Output mode is the standard PWM mode

discussed in Section 14.4 “Enhanced PWM Mode”.

The Half-Bridge and Full-Bridge Output modes are

covered in detail in the sections that follow.

The general relationship of the outputs in all

configurations is summarized in Figure 14-2.

TABLE 14-2: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 40 MHz

PWM Frequency

2.44 kHz 9.77 kHz 39.06 kHz 156.25 kHz 312.50 kHz 416.67 kHz

Timer Prescaler (1, 4, 16)

16

4

1

1

1

1

PR2 Value

FFh

FFh

FFh

3Fh

1Fh

17h

Maximum Resolution (bits)

10

10

10

8

7

6.58

DS39682C-page 134

Preliminary

© 2007 Microchip Technology Inc.

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