ATA6617 View Datasheet(PDF) - Atmel Corporation
Part Name
Description
MFG CO.
ATA6617
Atmel Corporation
'ATA6617' PDF : 308 Pages View PDF
Atmel ATA6616/ATA6617
4.5.1.1
CPU Clock – clkCPU
The CPU clock is routed to parts of the system concerned with the AVR® core operation.
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 perform-
ing general operations and calculations.
4.5.1.2
I/O Clock – clkI/O
The I/O clock is used by the majority of the I/O modules, like synchronous Timer/Counter. 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.
4.5.1.3
Flash Clock – clkFLASH
The Flash clock controls operation of the Flash interface. The Flash clock is usually active
simultaneously with the CPU clock.
4.5.1.4
Asynchronous Timer Clock – clkASY
The asynchronous timer clock allows the asynchronous Timer/Counter to be clocked directly
from an external clock or an external low frequency crystal. The dedicated clock domain
allows using this Timer/Counter as a real-time counter even when the device is in sleep mode.
4.5.1.5
ADC Clock – clkADC
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 accurate ADC
conversion results.
4.5.2
Clock Sources
The device has the following clock source options, selectable by Flash Fuse bits (default) or
by the CLKSELR register (dynamic clock switch circuit) as shown below. The clock from the
selected source is input to the AVR® clock generator, and routed to the appropriate modules.
Table 4-5. Device Clocking Options Select(1) versus PB4 and PB5 Functionality
Device Clocking Option
CKSEL3..0(2)
CSEL3..0(3)
PB4
PB5
External Clock
0000 b
CLKI
Calibrated Internal RC Oscillator 8.0MHz
0010 b
I/O
Watchdog Oscillator 128kHz
0011 b
I/O
External Low-frequency Oscillator
01xx b
XTAL1
External Crystal/Ceramic Resonator (0.4 - 0.9MHz)
100x b
XTAL1
External Crystal/Ceramic Resonator (0.9 - 3.0MHz)
101x b
XTAL1
External Crystal/Ceramic Resonator (3.0 - 8.0MHz)
110x b
XTAL1
External Crystal/Ceramic Resonator (8.0 - 16.0MHz)
111x b
XTAL1
Notes: 1. For all fuses “1” means unprogrammed while “0” means programmed
CLKO - I/O
CLKO - I/O
CLKO - I/O
XTAL2
XTAL2
XTAL2
XTAL2
XTAL2
2. Flash Fuse bits
3. CLKSELR register bits
The various choices for each clocking option are given in the following sections.
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