ATTINY26L8SU SL383 Atmel, ATTINY26L8SU SL383 Datasheet - Page 24

• Manufacturer Part Number: ATTINY26L8SU SL383
• Description: MCU 8-Bit ATtiny AVR RISC 2KB Flash 3.3V/5V 20-Pin SOIC T/R
• Manufacturer: Atmel

System Clock and
Clock Options
Clock Systems and their
Distribution
CPU Clock – clk
I/O Clock – clk
Flash Clock – clk
ADC Clock – clk
24
ATtiny26(L)
I/O
CPU
ADC
FLASH
Figure 20 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 “Power Management and Sleep Modes” on page 38. The clock systems
are detailed below.
Figure 20. Clock Distribution
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 Reg-
ister 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/Counters, and USI.
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 simultaneously with the CPU clock.
The ADC is provided with a dedicated clock domain. This allows halting the CPU and
I/O clocks in order to reduce noise generated by digital circuitry. This gives more accu-
rate ADC conversion results.
clk
Timer/Counter1
PCK
PLL
clk
PLL
External RC
General I/O
Oscillator
modules
clk
I/O
Multiplexer
External clock
Control Unit
AVR Clock
Clock
ADC
Source clock
clk
ADC
clk
Oscillator
clk
Crystal
CPU
FLASH
Reset Logic
CPU Core
Crystal Oscillator
Low-Frequency
Watchdog clock
RAM
Watchdog Timer
Watchdog
Oscillator
1477J–AVR–06/07
Calibrated RC
Flash and
EEPROM
Oscillator