PIC24FJ256GA106T-I Datasheet, PDF (158/292 Pages) Microchip Technology – 64/80/100-Pin, 16-Bit General Purpose Flash Microcontrollers with Peripheral Pin Select

PIC24FJ256GA110 FAMILY
FIGURE 13-2:
OUTPUT COMPARE BLOCK DIAGRAM (DOUBLE-BUFFERED, 16-BIT PWM MODE)
OCTSELx
SYNCSELx
TRIGSTAT
TRIGMODE
OCTRIG
OCxCON1
OCxCON2
OCxR
Rollover/Reset
OCxR buffer
OC Clock
Sources
Trigger and
Sync Sources
Clock
Select
Increment
Reset
Trigger and ^{Match Event}
Sync Logic
Comparator
OCxTMR
Match
Event
Rollover
Comparator
OCxRS buffer
Match
Event
OCMx
OCINV
OCTRIS
FLTOUT
FLTTRIEN
FLTMD
ENFLT0
OCFLT0
OC Output and
Fault Logic
OCx Pin
OCFA/OCFB
Reset
Rollover/Reset
OCxRS
OCx Interrupt
Note 1: The OCx outputs must be assigned to an available RPn pin before use. Please see Section 9.4 “Peripheral
Pin Select” for more information.
13.3.1 PWM PERIOD
The PWM period is specified by writing to PRy, the
Timer Period register. The PWM period can be
calculated using Equation 13-1.
EQUATION 13-1: CALCULATING THE PWM
PERIOD⁽¹⁾
PWM Period = [(PRy) + 1] • TCY • (Timer Prescale Value)
where: PWM Frequency = 1/[PWM Period]
Note 1: Based on TCY = TOSC * 2, Doze mode
and PLL are disabled.
Note:
A PRy value of N will produce a PWM
period of N + 1 time base count cycles. For
example, a value of 7 written into the PRy
register will yield a period consisting of
8 time base cycles.
13.3.2 PWM DUTY CYCLE
The PWM duty cycle is specified by writing to the
OCxRS and OCxR registers. The OCxRS and OCxR
registers can be written to at any time, but the duty
cycle value is not latched until a match between PRy
and TMRy occurs (i.e., the period is complete). This
provides a double buffer for the PWM duty cycle and is
essential for glitchless PWM operation.
Some important boundary parameters of the PWM duty
cycle include:
• If OCxR, OCxRS, and PRy are all loaded with
0000h, the OCx pin will remain low (0% duty
cycle).
• ·If OCxRS is greater than PRy, the pin will remain
high (100% duty cycle).
See Example 13-1 for PWM mode timing details.
Table 13-1 and Table 13-2 show example PWM
frequencies and resolutions for a device operating at
4 MIPS and 10 MIPS, respectively.
DS39905B-page 156
Preliminary
© 2008 Microchip Technology Inc.