Atmel Evaluation Kit for AT32uC3A0512, 32-Bit AVR Microcontroller Atmel ATEVK1105 ATEVK1105 Data Sheet
Product codes
ATEVK1105
681
AT32UC3A
32.6.3
PWM Controller Operations
32.6.3.1
Initialization
Before enabling the output channel, this channel must have been configured by the software
application:
• Configuration of the clock generator if DIVA and DIVB are required
• Selection of the clock for each channel (CPRE field in the CMRx register)
• Configuration of the waveform alignment for each channel (CALG field in the CMRx register)
• Configuration of the period for each channel (CPRD in the CPRDx register). Writing in CPRDx
• Configuration of the clock generator if DIVA and DIVB are required
• Selection of the clock for each channel (CPRE field in the CMRx register)
• Configuration of the waveform alignment for each channel (CALG field in the CMRx register)
• Configuration of the period for each channel (CPRD in the CPRDx register). Writing in CPRDx
Register is possible while the channel is disabled. After validation of the channel, the user must
use CUPDx Register to update CPRDx as explained below.
• Configuration of the duty cycle for each channel (CDTY in the CDTYx register). Writing in
CDTYx Register is possible while the channel is disabled. After validation of the channel, the
user must use CUPDx Register to update CDTYx as explained below.
• Configuration of the output waveform polarity for each channel (CPOL in the CMRx register)
• Enable Interrupts (Writing CHIDx in the IER register)
• Enable the PWM channel (Writing CHIDx in the ENA register)
It is possible to synchronize different channels by enabling them at the same time by means of
• Enable Interrupts (Writing CHIDx in the IER register)
• Enable the PWM channel (Writing CHIDx in the ENA register)
It is possible to synchronize different channels by enabling them at the same time by means of
writing simultaneously several CHIDx bits in the ENA register.
In such a situation, all channels may have the same clock selector configuration and the same
In such a situation, all channels may have the same clock selector configuration and the same
period specified.
32.6.3.2
Source Clock Selection Criteria
The large number of source clocks can make selection difficult. The relationship between the
value in the Period Register (CPRDx) and the Duty Cycle Register (CDTYx) can help the user in
choosing. The event number written in the Period Register gives the PWM accuracy. The Duty
Cycle quantum cannot be lower than
1/CPRDx
value. The higher the value of CPRDx, the
greater the PWM accuracy.
For example, if the user sets 15 (in decimal) in CPRDx, the user is able to set a value between 1
For example, if the user sets 15 (in decimal) in CPRDx, the user is able to set a value between 1
up to 14 in CDTYx Register. The resulting duty cycle quantum cannot be lower than 1/15 of the
PWM period.
32.6.3.3
Changing the Duty Cycle or the Period
It is possible to modulate the output waveform duty cycle or period.
To prevent unexpected output waveform, the user must use the update register (PWM_CUPDx)
To prevent unexpected output waveform, the user must use the update register (PWM_CUPDx)
to change waveform parameters while the channel is still enabled. The user can write a new
period value or duty cycle value in the update register (CUPDx). This register holds the new
value until the end of the current cycle and updates the value for the next cycle. Depending on
the CPD field in the CMRx register, CUPDx either updates CPRDx or CDTYx. Note that even if
the update register is used, the period must not be smaller than the duty cycle.
32058K
AVR32-01/12