AT90CAN128 datasheet(37/431 Pages) ATMEL

37 / 431 page

7682C–AUTO–04/08

AT90CAN32/64/128

System Clock

5.1

Clock Systems and their Distribution

Figure 5-1 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 unused

modules can be halted by using different sleep modes, as described in “Power Management and

Sleep Modes” on page 46. The clock systems are detailed below.

Figure 5-1.

Clock Distribution

5.1.1

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.

5.1.2

I/O Clock – clkI/O

The I/O clock is used by the majority of the I/O modules, like Timer/Counters, SPI, CAN,

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 address recognition in the TWI module is carried out asynchro-

nously when clkI/O is halted, enabling TWI address reception in all sleep modes.

5.1.3

Flash Clock – clkFLASH

The Flash clock controls operation of the Flash interface. The Flash clock is usually active simul-

taneously with the CPU clock.

General I/O

Modules

CAN

Controller

CPU Core

RAM

clk

I/O

clk

ASY

AVR Clock

Control Unit

clk

CPU

Flash and

EEPROM

clk

FLASH

Source clock

Watchdog

Timer

Watchdog

Oscillator

Reset

Logic

Prescaler

Clock

Multiplexer

CKOUT Fuse

CLKO

Watchdog clock

Calibrated RC

Oscillator

Timer/Counter2

Oscillator

External Clock

Crystal

Oscillator

Low-frequency

Crystal Oscillator

External Clock

ADC

clk

ADC

Asynchronous

Timer/Counter2

TOSC2

XTAL2

TOSC1

XTAL1

AT90CAN128 Datasheet(PDF) 37 Page - ATMEL Corporation

AT90CAN128 Datasheet(HTML) 37 Page - ATMEL Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL