ATA6612C View Datasheet(PDF) - Atmel Corporation
Part Name
Description
MFG CO.
ATA6612C
Atmel Corporation
'ATA6612C' PDF : 312 Pages View PDF
5.6 System Clock and Clock Options
5.6.1
Clock Systems and their Distribution
Figure 5-11 presents the principal clock systems in the AVR® and their distribution. All of the clocks need not be active at a
given time. In order to reduce power consumption, the clocks to modules not being used can be halted by using different
sleep modes, as described in Section 5.7 “Power Management and Sleep Modes” on page 55. The clock systems are
detailed below.
Figure 5-11. Clock Distribution
Asynchronous
Timer/Counter
General I/O
Modules
ADC
CPU Core
RAM
Flash and
EEPROM
clkI/O
clkASY
clkADC
AVR Clock
Control Unit
System Clock
Prescaler
clkCPU
clkFLASH
Reset Logic
Watchdog Timer
Source clock
Clock
Multiplexer
Watchdog clock
Watchdog
Oscillator
Timer/Counter
Oscillator
External Clock
Crystal
Oscillator
Low Frequency
Crystal Oscillator
Calibrated RC
Oscillator
5.6.1.1 CPU Clock – clkCPU
The CPU clock is routed to parts of the system concerned with operation of the AVR core. Examples of such modules are
the general purpose register file, the status register and the data memory holding the stack pointer. Halting the CPU clock
inhibits the core from performing general operations and calculations.
5.6.1.2 I/O Clock – clkI/O
The I/O clock is used by the majority of the I/O modules, like Timer/Counters, SPI, and USART. The I/O clock is also used by
the external interrupt module, but note that some external interrupts are detected by asynchronous logic, allowing such
interrupts to be detected even if the I/O clock is halted. Also note that start condition detection in the USI module is carried
out asynchronously when clkI/O is halted, TWI address recognition in all sleep modes.
5.6.1.3 Flash Clock – clkFLASH
The flash clock controls operation of the flash interface. The flash clock is usually active simultaneously with the CPU clock.
5.6.1.4 Asynchronous Timer Clock – clkASY
The asynchronous timer clock allows the asynchronous Timer/Counter to be clocked directly from an external clock or an
external 32kHz clock crystal. The dedicated clock domain allows using this Timer/Counter as a real-time counter even when
the device is in sleep mode.
46 ATA6612C/ATA6613C [DATASHEET]
9111L–AUTO–11/14
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