PIC16F631/677/685/687/689/690
The PWM output (Figure 11-4) has a time base
(period) and a time that the output stays high (duty
cycle).
11.3 PWM Mode
The PWM mode generates a Pulse-Width Modulated
signal on the CCP1 pin. The duty cycle, period and
resolution are determined by the following registers:
FIGURE 11-4:
CCP PWM OUTPUT
• PR2
Period
• T2CON
• CCPR1L
• CCP1CON
Pulse Width
TMR2 = PR2
TMR2 = CCPR1L:CCP1CON<5:4>
In Pulse-Width Modulation (PWM) mode, the CCP
module produces up to a 10-bit resolution PWM output
on the CCP1 pin. Since the CCP1 pin is multiplexed
with the PORT data latch, the TRIS for that pin must be
cleared to enable the CCP1 pin output driver.
TMR2 = 0
Note:
Clearing the CCP1CON register will
relinquish CCP1 control of the CCP1 pin.
Figure 11-3 shows a simplified block diagram of PWM
operation.
Figure 11-4 shows a typical waveform of the PWM
signal.
For a step-by-step procedure on how to set up the CCP
module for PWM operation, see Section 11.3.7
“Setup for PWM Operation”.
FIGURE 11-3:
SIMPLIFIED PWM BLOCK
DIAGRAM
CCP1CON<5:4>
Duty Cycle Registers
CCPR1L
CCPR1H(2) (Slave)
Comparator
CCP1
R
S
Q
(1)
TMR2
TRIS
Comparator
PR2
Clear Timer2,
toggle CCP1 pin and
latch duty cycle
Note 1: The 8-bit timer TMR2 register is concatenated
with the 2-bit internal system clock (FOSC), or
2 bits of the prescaler, to create the 10-bit time
base.
2: In PWM mode, CCPR1H is a read-only register.
DS41262D-page 130
© 2007 Microchip Technology Inc.
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