ATMEGA8-16AI SL383 Atmel, ATMEGA8-16AI SL383 Datasheet - Page 25

• Manufacturer Part Number: ATMEGA8-16AI SL383
• Description: Semiconductors and Actives, Microprocessors, Microcontrollers
• Manufacturer: Atmel

System Clock
and Clock
Options
Clock Systems
and their
Distribution
CPU Clock – clk
I/O Clock – clk
Flash Clock – clk
2486W–AVR–02/10
I/O
CPU
FLASH
Figure 10
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 10. 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 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/Counters, SPI, and USART.
The I/O clock is also used by the External Interrupt module, but note that some external inter-
rupts are detected by asynchronous logic, allowing such interrupts to be detected even if the I/O
clock is halted. Also note that address recognition in the TWI module is carried out asynchro-
nously when clk
The Flash clock controls operation of the Flash interface. The Flash clock is usually active simul-
taneously with the CPU clock.
Timer/Counter
Timer/Counter
Asynchronous
Oscillator
presents the principal clock systems in the AVR and their distribution. All of the clocks
I/O
is halted, enabling TWI address reception in all sleep modes.
General I/O
External RC
Modules
Oscillator
clk
clk
ASY
I/O
33. The clock systems are detailed
External Clock
Control Unit
AVR Clock
Multiplexer
Clock
ADC
clk
Source Clock
ADC
CPU Core
Reset Logic
clk
Oscillator
clk
Crystal
CPU
FLASH
Watchdog Clock
Crystal Oscillator
Low-Frequency
Watchdog Timer
Figure
Watchdog
Oscillator
RAM
ATmega8(L)
10.
“Power Manage-
Calibrated RC
Flash and
EEPROM
Oscillator
25