atmega32c1 ATMEL Corporation, atmega32c1 Datasheet - Page 29

• Manufacturer Part Number: atmega32c1
• Description: Atmega32m1 Automotive 8-bit Avr Microcontroller With 32k/64k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

5. System Clock
5.1
5.1.1
5.1.2
5.1.3
7647A–AVR–02/08
Clock Systems and their Distribution
CPU Clock – clk
I/O Clock – clk
Flash Clock – clk
I/O
Figure 5-1
need not be active at a given time. In order to reduce power consumption, the clocks to unused
modules can be halted by using different sleep modes, as described in
Sleep Modes” on page
Figure 5-1.
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/Counters, SPI, UART. 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
presents the principal clock systems in the AVR and their distribution. All of the clocks
Fast
Peripherals
Clock Distribution
PLL
CLK
PLL
39. The clock systems are detailed below.
General I/O
Modules
clk
I/O
External Clock
Multiplexer
ADC
Control Unit
AVR Clock
Clock
clk
ADC
Source Clock
Oscillator)
(Crystal
CPU Core
clk
clk
ATmega32/64/M1/C1
CPU
FLASH
Reset Logic
Watchdog Clock
RAM
Watchdog
Oscillator
Watchdog Timer
“Power Management and
Flash and
EEPROM
Calibrated RC
Oscillator
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