DSPIC30F2010 datasheet(84/202 Pages) MICROCHIP

84 / 202 page

dsPIC30F2010

DS70118J-page 84

14.1.4

DOUBLE UPDATE MODE

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 func-

tions to the user. First, the control loop bandwidth is

doubled because the PWM duty cycles can be

updated, twice per period. Second, asymmetrical cen-

ter-aligned PWM waveforms can be generated, which

are useful for minimizing output waveform distortion in

certain motor control applications.

14.1.5

PWM TIME BASE PRESCALER

The input clock to PTMR (FOSC/4), has prescaler

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.

14.1.6

PWM TIME BASE POSTSCALER

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.

14.2

PWM Period

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

PTMR register is reset to zero after a match with

the PTPER register.

• 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

PWM

period

can

determined

using

Equation 14-1:

EQUATION 14-1:

PWM PERIOD

If the PWM time base is configured for one of the Up/

Down Count modes, the PWM period is found using

Equation 14-2.

EQUATION 14-2:

PWM PERIOD (UP/DOWN

COUNT MODE)

The maximum resolution (in bits) for a given device

oscillator and PWM frequency can be determined using

Equation 14-3:

EQUATION 14-3:

PWM RESOLUTION

Note:

Programming a value of 0x0001 in the

period register could generate a continu-

ous interrupt pulse, and hence, must be

avoided.

TPWM = TCY

• (PTPER + 1) • PTMR Prescale Value

TPWM = TCY

• 2 • (PTPER + 1) • PTMR Prescale Value

Resolution =

log (2

• TPWM/TCY)

log (2)

DSPIC30F2010 датащи(PDF) 84 Page - Microchip Technology

DSPIC30F2010 датащи(HTML) 84 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

датащи скачать

ссылки URL