Information

 2010 Microchip Technology Inc. DS41303G-page 175
PIC18F2XK20/4XK20
16.4 PWM (Enhanced Mode)
The Enhanced PWM Mode can generate a PWM signal
on up to four different output pins with up to 10-bits of
resolution. It can do this through four different PWM
output modes:
• Single PWM
• Half-Bridge PWM
• Full-Bridge PWM, Forward mode
• Full-Bridge PWM, Reverse mode
To select an Enhanced PWM mode, the P1M bits of the
CCP1CON register must be set appropriately.
The PWM outputs are multiplexed with I/O pins and are
designated P1A, P1B, P1C and P1D. The polarity of the
PWM pins is configurable and is selected by setting the
CCP1M bits in the CCP1CON register appropriately.
Table 16-1 shows the pin assignments for each
Enhanced PWM mode.
Figure 16-1 shows an example of a simplified block
diagram of the Enhanced PWM module.
FIGURE 16-1: EXAMPLE SIMPLIFIED BLOCK DIAGRAM OF THE ENHANCED PWM MODE
TABLE 16-1: EXAMPLE PIN ASSIGNMENTS FOR VARIOUS PWM ENHANCED MODES
Note: The PWM Enhanced mode is available on
the Enhanced Capture/Compare/PWM
module (CCP1) only.
Note: To prevent the generation of an
incomplete waveform when the PWM is
first enabled, the ECCP module waits until
the start of a new PWM period before
generating a PWM signal.
CCPR1L
CCPR1H (Slave)
Comparator
TMR2
Comparator
PR2
(1)
RQ
S
Duty Cycle Registers
DC1B<1:0>
Clear Timer2,
toggle PWM pin and
latch duty cycle
Note 1: The 8-bit timer TMR2 register is concatenated with the 2-bit internal Q clock, or 2 bits of the prescaler to create the 10-bit
time base.
TRIS
CCP1/P1A
TRIS
P1B
TRIS
P1C
TRIS
P1D
Output
Controller
P1M<1:0>
2
CCP1M<3:0>
4
PWM1CON
CCP1/P1A
P1B
P1C
P1D
Note 1: The TRIS register value for each PWM output must be configured appropriately.
2: Clearing the CCPxCON register will relinquish ECCP control of all PWM output pins.
3: Any pin not used by an Enhanced PWM mode is available for alternate pin functions.
ECCP Mode P1M<1:0> CCP1/P1A P1B P1C P1D
Single 00 Yes
(1)
Yes
(1)
Yes
(1)
Yes
(1)
Half-Bridge 10 Yes Yes No No
Full-Bridge, Forward 01 Yes Yes Yes Yes
Full-Bridge, Reverse 11 Yes Yes Yes Yes
Note 1: Outputs are enabled by pulse steering in Single mode. See Register 16-4.