AT89C5131A-RDTUM datasheet(13/184 Pages) ATMEL

13 / 184 page

AT89C5130A/31A-M

4337C–USB–02/05

Clock Controller

Introduction

The AT89C5130A/31A-M clock controller is based on an on-chip oscillator feeding an

on-chip Phase Lock Loop (PLL). All the internal clocks to the peripherals and CPU core

are generated by this controller.

The AT89C5130A/31A-M X1 and X2 pins are the input and the output of a single-stage

on-chip inverter (see Figure 5) that can be configured with off-chip components as a

Pierce oscillator (see Figure 6). Value of capacitors and crystal characteristics are

detailed in the section “DC Characteristics”.

The X1 pin can also be used as input for an external 48 MHz clock.

The clock controller outputs three different clocks as shown in Figure 5:

•

a clock for the CPU core

•

a clock for the peripherals which is used to generate the Timers, PCA, WD, and Port

sampling clocks

•

a clock for the USB controller

These clocks are enabled or disabled depending on the power reduction mode as

detailed in Section “Power Management”, page 153.

Figure 5. Oscillator Block Diagram

Oscillator

Two clock sources are available for CPU:

•

Crystal oscillator on X1 and X2 pins: Up to 32 MHz

•

External 48 MHz clock on X1 pin

In order to optimize the power consumption, the oscillator inverter is inactive when the

PLL output is not selected for the USB device.

PCON.1

IDL

PCON.0

Peripheral

CPU Core

CKCON.0

÷ 2

Clock

EXT48

PLLCON.2

PLL

USB

Clock

AT89C5131A-RDTUM 데이터시트(PDF) 13 Page - ATMEL Corporation

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