DSPIC30F3011 Microchip Technology Inc., DSPIC30F3011 Datasheet - Page 96

• Manufacturer Part Number: DSPIC30F3011
• Description: Dspic30f3010/3011 Enhanced Flash 16-bit Digital Signal Controller
• Manufacturer: Microchip Technology Inc.

dsPIC30F3010/3011
15.1.4
In the Double-Update mode (PTMOD<1:0> = 11), an
interrupt event is generated each time the PTMR regis-
ter is equal to zero, as well as each time a period match
occurs. The postscaler selection bits have no effect in
this mode of the timer.
The Double-Update mode provides two additional
functions to the user. First, the control loop bandwidth
is doubled because the PWM duty cycles can be
updated, twice per period. Second, asymmetrical
center-aligned PWM waveforms can be generated,
which are useful for minimizing output waveform
distortion in certain motor control applications.
15.1.5
The input clock to PTMR (F
options of 1:1, 1:4, 1:16, or 1:64, selected by control
bits PTCKPS<1:0> in the PTCON SFR. The prescaler
counter is cleared when any of the following occurs:
• a write to the PTMR register
• a write to the PTCON register
• any device Reset
The PTMR register is not cleared when PTCON is
written.
15.1.6
The match output of PTMR can optionally be post-
scaled through a 4-bit postscaler (which gives a 1:1 to
1:16 scaling).
The postscaler counter is cleared when any of the
following occurs:
• a write to the PTMR register
• a write to the PTCON register
• any device Reset
The PTMR register is not cleared when PTCON is written.
DS70141D-page 94
Note:
DOUBLE-UPDATE MODE
Programming a value of 0x0001 in the
period register could generate a continu-
ous interrupt pulse, and hence, must be
avoided.
PWM TIME BASE PRESCALER
PWM TIME BASE POSTSCALER
OSC
/4), has prescaler
Confidential
15.2
PTPER is a 15-bit register and is used to set the count-
ing period for the PWM time base. PTPER is a double-
buffered register. The PTPER buffer contents are
loaded into the PTPER register at the following
instances:
• Free-Running and Single-Shot modes: When the
• Up/Down Counting modes: When the PTMR
The value held in the PTPER buffer is automatically
loaded into the PTPER register when the PWM time
base is disabled (PTEN = 0).
The
Equation 15-1:
EQUATION 15-1:
If the PWM time base is configured for one of the Up/
Down Count modes, the PWM period is given by
Equation 15-2.
EQUATION 15-2:
The maximum resolution (in bits) for a given device
oscillator and PWM frequency can be determined using
Equation 15-3:
EQUATION 15-3:
PTMR register is reset to zero after a match with
the PTPER register.
register is zero.
PWM
Resolution =
PWM Period
T
T
PWM
PWM
period
=
=
2
(PTMR Prescale Value)
•
(PTMR Prescale Value)
T
T
PWM PERIOD (FREE-
RUNNING MODE)
PWM PERIOD (UP/DOWN
COUNTING MODE)
PWM RESOLUTION
CY
CY
can
© 2007 Microchip Technology Inc.
log (2
•
•
(PTPER + 0.75)
(PTPER + 1)
log (2)
be
•
T
PWM
determined
/ T
CY
)
using