AT83SND2CMP3 datasheet(10/97 Pages) ATMEL

10 / 97 page

AT83SND2CMP3

7524B–MP3–05/06

Clock Controller

The clock controller is based on an on-chip oscillator feeding an on-chip Phase Lock

Loop (PLL). All internal clocks to the peripherals and CPU core are generated by this

controller.

Oscillator

The X1 and X2 pins are the input and the output of a single-stage on-chip inverter (see

Figure 4) that can be configured with off-chip components such as a Pierce oscillator

(see Figure 5). Value of capacitors and crystal characteristics are detailed in the section

“DC Characteristics”.

The oscillator outputs three different clocks: a clock for the PLL, a clock for the CPU

core, and a clock for the peripherals as shown in Figure 4. These clocks are either

enabled or disabled, depending on the power reduction mode as detailed in the section.

The peripheral clock is used to generate the Timer 0, Timer 1, MMC, SPI, and Port sam-

pling clocks.

Figure 4. Oscillator Block Diagram and Symbol

Figure 5. Crystal Connection

PLL

PLL Description

The PLL is used to generate internal high frequency clock (the PLL Clock) synchronized

with an external low-frequency (the Oscillator Clock). The PLL clock provides the MP3

decoder, the audio interface, and the USB interface clocks. Figure 6 shows the internal

structure of the PLL.

The PFLD block is the Phase Frequency Comparator and Lock Detector. This block

makes the comparison between the reference clock coming from the N divider and the

reverse clock coming from the R divider and generates some pulses on the Up or Down

signal depending on the edge position of the reverse clock. The PLLEN bit in PLLCON

The CHP block is the Charge Pump that generates the voltage reference for the VCO by

injecting or extracting charges from the external filter connected on PFILT pin (see

PCON.1

IDL

PCON.0

Peripheral

CPU Core

CKCON.0

÷ 2

PER

CLOCK

Clock

Peripheral Clock Symbol

CPU

CLOCK

CPU Core Clock Symbol

OSC

CLOCK

Oscillator Clock Symbol

Oscillator

Clock

VSS

AT83SND2CMP3 Datasheet(PDF) 10 Page - ATMEL Corporation

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