SCF5250 datasheet(7/48 Pages) MOTOROLA

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Introduction

SCF5250 Integrated ColdFire® Microprocessor Data Sheet, Rev. 1.1

Freescale Semiconductor

1.2.24 Crystal and On-chip PLL

Typically, an external 16.92 Mhz or 33.86 Mhz clock input is used for CD R/W applications, while an

11.2896 MHz clock is more practical for Portable CD player applications. However, the on-chip

programmable PLL, which generates the processor clock, allows the use of almost any low frequency

external clock (5-35 Mhz).

Two clock outputs (MCLK1 and MCLK2) are provided for use as Audio Master Clock. The output

frequencies of both outputs are programmable to Fxtal, Fxtal/2, Fxtal/3, and Fxtal/4. The Fxtal/3 option is

only available when the 33.86 Mhz crystal is connected.

The SCF5250 supports VCO operation of the oscillator by means of a 16-bit pulse density modulation

output. Using this mode, it is possible to lock the oscillator to the frequency of an incoming IEC958 or IIS

signal. The maximum trim depends on the type and design of the oscillator. Typically a trim of +/- 100

ppm can be achieved with a crystal oscillator and over +/- 1000 ppm with an LC oscillator.

1.2.25 Boot ROM

The boot ROM on the SCF5250 serves to boot the CPU in designs which do not have external Flash

memory or ROM. Typically this occurs in systems which have a separate MCU to control the system,

and/or the SCF5250 is used as a stand-alone decoder.

The SCF5250 can be booted in one of three modes:

•

External ROM

•

Internal ROM Master mode – boots from I2C, SPI, or IDE

•

Internal ROM Slave mode – boots from I2C or UART

1.2.26 Voltage Regulator

The SCF5250 contains an on-chip linear regulator that generates 1.2V from a 3.3V input. The regulator is

self-contained and drives the 1.2V core voltage out on one pin that can be used to power the core supply

pins at the board level. In battery powered portable applications, it is recommended that an external dc-dc

converter be used to generate the 1.2V core voltage to minimize power consumption.

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