Atmel AT32UC3 Series, Application Note

11

32094B–AVR32–05/09

AVR32710

6.2.1

Pulse Width Modulation Generation

6.2.1.1

Using PWM module

The AVR32 UC3 is able to generate PWM signals through a dedicated PWM module or through
the Timer Counter used. The PWM module is used in this application

 (1)

 .

•

We need first to setup alternate functions of GPIO corresponding to alternate pins/functions 
used for PWM channels.

•

PWM module is configured in center aligned mode or left aligned mode. We will only 
consider PWM module in center aligned mode to fit with S.V.P.W.M implementation. To 
configure this mode, we need to set: 
–

CALG bifield in CMRx register at ‘1’ (fixed value)

•

The PWM module has its own global prescaler.
–

PREA,PREB bitfield in PWM.MR register

•

Each PWM channels has its own prescaler as well. It is possible to define a different period 
for a given channel 

x

.

–

CPRE bitfield in PWM.CMR

x

 register

•

The PWM period and duty cycle is configured from this prescaled period:
–

CPRD bitfield in CMRx register

–

CDTY bitfield in CMRx register

•

Finally enable PWM channel
–

CHIDx id in ENA register

Figure 6-3.

PWM Channel in center aligned mode

Let’s take the following example:

1.

Refer to UC3 datasheet section PWM for more details

Table 6-2.

PWM calculation example

PBA(MHz)

CMRx.CPRE

MR.DIVA

MR.DIVB

CPRDx

PWM(Hz)

24

1

0

0

256

23437

CounterValue

Value

CDTY

PWMx

PWM in

Center Aligned Mode

UH

UL

YH

YL

ZL

ZH

HallA

HallB

HallC

BLDC

Hall Sensors

CPRD

)

(

2

s

PBA

CPRDxDIVA

PERIOD

×

=