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ManualsBrandsMICROCHIP TECHNOLOGY ManualsMicrocontrollers, Microprocessors & QuartzesEmbedded microcontroller SPDIP 28 16-Bit 20 null I/O number 20
81828384858687888990
© 2011 Microchip Technology Inc. DS70118J-page 85
dsPIC30F2010
14.3 Edge-Aligned PWM
Edge-aligned PWM signals are produced by the mod-
ule when the PWM time base is in the Free Running or
Single Shot mode. For edge-aligned PWM outputs, the
output has a period specified by the value in PTPER
and a duty cycle specified by the appropriate duty cycle
register (see Figure 14-2). The PWM output is driven
active at the beginning of the period (PTMR = 0) and is
driven inactive when the value in the duty cycle register
matches PTMR.
If the value in a particular duty cycle register is zero,
then the output on the corresponding PWM pin will be
inactive for the entire PWM period. In addition, the out-
put on the PWM pin will be active for the entire PWM
period if the value in the duty cycle register is greater
than the value held in the PTPER register.
FIGURE 14-2: EDGE-ALIGNED PWM
14.4 Center-Aligned PWM
Center-aligned PWM signals are produced by the
module when the PWM time base is configured in an
Up/Down Counting mode (see Figure 14-3).
The PWM compare output is driven to the active state
when the value of the duty cycle register matches the
value of PTMR and the PWM time base is counting
downwards (PTDIR = 1). The PWM compare output is
driven to the inactive state when the PWM time base is
counting upwards (PTDIR = 0) and the value in the
PTMR register matches the duty cycle value.
If the value in a particular duty cycle register is zero,
then the output on the corresponding PWM pin will be
inactive for the entire PWM period. In addition, the out-
put on the PWM pin will be active for the entire PWM
period if the value in the duty cycle register is equal to
the value held in the PTPER register.
FIGURE 14-3: CENTER-ALIGNED PWM
14.5 PWM Duty Cycle Comparison
Units
There are four 16-bit Special Function Registers
(PDC1, PDC2, PDC3 and PDC4) used to specify duty
cycle values for the PWM module.
The value in each duty cycle register determines the
amount of time that the PWM output is in the active
state. The duty cycle registers are 16 bits wide. The
LSb of a duty cycle register determines whether the
PWM edge occurs in the beginning. Thus, the PWM
resolution is effectively doubled.