PIC18F2682-I/PT MICROCHIP [Microchip Technology], PIC18F2682-I/PT Datasheet - Page 172

• Manufacturer Part Number: PIC18F2682-I/PT
• Description: 28/40/44-Pin Enhanced Flash Microcontrollers with ECAN Technology, 10-Bit A/D and nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F2682/2685/4682/4685
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
operation.
When the CCPR1H and 2-bit latch match TMR2,
concatenated with an internal 2-bit Q clock or 2 bits of
the TMR2 prescaler, the CCP1 pin is cleared.
The maximum PWM resolution (bits) for a given PWM
frequency is given by the equation.
TABLE 15-4:
15.4.3
The PWM auto-shutdown features of the Enhanced
CCP1 module are available to ECCP1 in PIC18F4682/
4685 (40/44-pin) devices. The operation of this feature
is discussed in detail in Section 16.4.7 “Enhanced
PWM Auto-Shutdown”.
Auto-shutdown features are not available for CCP1.
DS39761B-page 170
Timer Prescaler (1, 4, 16)
PR2 Value
Maximum Resolution (bits)
PWM Frequency
PWM AUTO-SHUTDOWN
(ECCP1 ONLY)
EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 40 MHz
2.44 kHz
FFh
16
14
9.77 kHz
Preliminary
FFh
12
4
39.06 kHz
EQUATION 15-3:
15.4.4
The following steps should be taken when configuring
the CCP1 module for PWM operation:
1.
2.
3.
4.
5.
Note:
FFh
10
1
Set the PWM period by writing to the PR2
register.
Set the PWM duty cycle by writing to the
CCPR1L register and CCP1CON<5:4> bits.
Make the CCP1 pin an output by clearing the
appropriate TRIS bit.
Set the TMR2 prescale value, then enable
Timer2 by writing to T2CON.
Configure the CCP1 module for PWM operation.
PWM Resolution (max) =
If the PWM duty cycle value is longer than
the PWM period, the CCP1 pin will not be
cleared.
SETUP FOR PWM OPERATION
156.25 kHz
3Fh
1
8
© 2007 Microchip Technology Inc.
312.50 kHz
log
1Fh
1
7
⎛
⎝
log(2)
F
F
PWM
OSC
⎞
⎠
416.67 kHz
bits
6.58
17h
1