attiny25v ATMEL Corporation, attiny25v Datasheet - Page 23

• Manufacturer Part Number: attiny25v
• Description: Microcontroller With 2/4/8k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

6. System Clock and Clock Options
6.1
6.1.1
6.1.2
6.1.3
2586K–AVR–01/08
Clock Systems and their Distribution
CPU Clock – clk
I/O Clock – clk
Flash Clock – clk
I/O
Figure 6-1
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
ment and Sleep Modes” on page
Figure 6-1.
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.
The I/O clock is used by the majority of the I/O modules, like Timer/Counter. 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.
The Flash clock controls operation of the Flash interface. The Flash clock is usually active simul-
taneously with the CPU clock.
CPU
FLASH
ADC
External Clock
clk
clk
presents the principal clock systems in the AVR and their distribution. All of the clocks
ADC
I/O
Clock Distribution
Source clock
System Clock
Control Unit
AVR Clock
Multiplexer
General I/O
Prescaler
Modules
Clock
Calibrated RC
Oscillator
Oscillator
Crystal
Reset Logic
35. The clock systems are detailed below.
clk
clk
Watchdog clock
clk
PCK
CPU
FLASH
Crystal Oscillator
Low-Frequency
CPU Core
Watchdog Timer
Watchdog
Oscillator
RAM
ATtiny25/45/85
Oscillator
PLL
Flash and
EEPROM
“Power Manage-
Calibrated RC
Oscillator
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