Datasheet

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483
SAM7S Series [DATASHEET]
6175M–ATARM–26-Oct-12
34.5.1 PWM Clock Generator
Figure 34-2. Functional View of the Clock Generator Block Diagram
Caution: Before using the PWM macrocell, the programmer must first enable the PWM clock in the Power Man-
agement Controller (PMC).
The PWM macrocell master clock, MCK, is divided in the clock generator module to provide different clocks avail-
able for all channels. Each channel can independently select one of the divided clocks.
The clock generator is divided in three blocks:
a modulo n counter which provides 11 clocks: F
MCK
, F
MCK
/2, F
MCK
/4, F
MCK
/8, F
MCK
/16, F
MCK
/32,
F
MCK
/64, F
MCK
/128, F
MCK
/256, F
MCK
/512, F
MCK
/1024
two linear dividers (1, 1/2, 1/3, ... 1/255) that provide two separate clocks: clkA and clkB
Each linear divider can independently divide one of the clocks of the modulo n counter. The selection of the clock
to be divided is made according to the PREA (PREB) field of the PWM Mode register (PWM_MR). The resulting
clock clkA (clkB) is the clock selected divided by DIVA (DIVB) field value in the PWM Mode register (PWM_MR).
After a reset of the PWM controller, DIVA (DIVB) and PREA (PREB) in the PWM Mode register are set to 0. This
implies that after reset clkA (clkB) are turned off.
modulo n counter
MCK
MCK/2
MCK/4
MCK/16
MCK/32
MCK/64
MCK/8
Divider A clkA
DIVA
PWM_MR
MCK
MCK/128
MCK/256
MCK/512
MCK/1024
PREA
Divider B clkB
DIVB
PWM_MR
PREB