AT90USB1286-16MU ATMEL [ATMEL Corporation], AT90USB1286-16MU Datasheet - Page 38

• Manufacturer Part Number: AT90USB1286-16MU
• Description: Microcontroller with 64/128K Bytes of ISP Flash and USB Controller
• Manufacturer: ATMEL [ATMEL Corporation]

6. System Clock and Clock Options
6.1
6.1.1
6.1.2
6.1.3
38
Clock Systems and their Distribution
AT90USB64/128
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/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 start condition detection in the USI 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.
CPU
FLASH
PLL Clock
USB PLL
Prescaler
USB
presents the principal clock systems in the AVR and their distribution. All of the clocks
X24
clk
clk
clk
Pllin (2MHz)
USB (48MHz)
XTAL (2-16 MHz)
Clock Distribution
I/O
is halted, TWI address recognition in all sleep modes.
Timer/Counter
Timer/Counter
Asynchronous
Oscillator
52. The clock systems are detailed below.
General I/O
Modules
clk
clk
Oscillator
ASY
I/O
Crystal
System Clock
Control Unit
AVR Clock
Multiplexer
Prescaler
Clock
ADC
External Clock
Source clock
clk
ADC
CPU Core
clk
clk
Reset Logic
CPU
FLASH
Watchdog clock
Watchdog
Oscillator
Watchdog Timer
RAM
“Power Manage-
Calibrated RC
7593A–AVR–02/06
Flash and
EEPROM
Oscillator