AT32UC3C2512C Automotive Atmel Corporation, AT32UC3C2512C Automotive Datasheet - Page 51

• Manufacturer Part Number: AT32UC3C2512C Automotive
• Manufacturer: Atmel Corporation

7.6
7.6.1
Figure 7-2.
7.6.1.1
7.6.1.2
9166C–AVR-08/11
Main Clock
Sources
Functional Description
Synchronous Clocks
Selecting the main clock source
Selecting synchronous clock division ratio
Synchronous Clock Generation
MCSEL
The System RC Oscillator (RCSYS) or a set of other clock sources provide the source for the
main clock, which is the common root for the synchronous clocks for the CPU/HSB and PBx
modules. For details about the other main clock sources, please refer to the register description
of the Main Clock Control Register (MCCTRL). The main clock is divided by an 8-bit prescaler,
and each of these synchronous clocks can run from any tapping of this prescaler, or the undi-
vided main clock, as long as f
fly, responding to varying load in the application. The clock domains can be shut down in sleep
mode, as described in
nous clock domain can be individually masked, to avoid power consumption in inactive modules.
The common main clock can be connected to RCSYS or a set of other clock sources. For details
about the other main clock sources, please refer to the register description of the Main Clock
Control Register (MCCTRL). By default, the main clock will be connected to RCSYS. The user
can connect the main clock to an other source by writing the MCSEL field in the MCCTRL regis-
ter. This must only be done after that unit has been enabled and is ready, otherwise a deadlock
will occur. Care should also be taken that the new frequency of the synchronous clocks does not
exceed the maximum frequency for each clock domain.
The main clock feeds an 8-bit prescaler, which can be used to generate the synchronous clocks.
By default, the synchronous clocks run on the undivided main clock. The user can select a pres-
caler division for the CPU clock by writing CPUDIV in CPUSEL register to one and CPUSEL in
CPUSEL register to the value, resulting in a CPU clock frequency:
Prescaler
f
CPU
= f
Instruction
main
Sleep
/ 2
(CPUSEL+1)
CPUSEL
Section
CPUDIV
CPU
7.6.3. Additionally, the clocks for each module in each synchro-
0
1
≥ f
Controller
Main Clock
PBx,
Sleep
. The synchronous clock source can be changed on-the
CPUMASK
Mask
AT32UC3C
CPU Clocks
HSB Clocks
PBx Clocks
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