Motorola Espresso Maker MC68340 User Manual

MOTOROLA

10-1

This section provides guidelines for using the MC68340. Minimum system-configuration
requirements and memory interface information are discussed.

One of the powerful features of the MC68340 is the small number of external components
needed to create an entire system. The information contained in the following paragraphs
details a simple high-performance MC68340 system (see Figure 10-1). This system
configuration features the following hardware:

• Processor Clock Circuitry

• Reset Circuitry

• SRAM Interface

• ROM Interface

• Serial Interface

CLOCK

CIRCUITRY

MC68340

SRAM

ROM

  SERIAL 

INTERFACE

The MC68340 has an on-chip clock synthesizer that can operate from an on-chip phase-
locked loop (PLL) and a voltage-controlled oscillator (VCO). The clock synthesizer uses
an external crystal connected between the EXTAL and XTAL pins as a reference
frequency source. Figure 10-2 shows a typical circuit using an inexpensive 32.768-kHz
watch crystal. The 20-M resistor connected between the EXTAL and XTAL pins provides
biasing for a faster oscillator startup time. The crystal manufacturer's documentation
should be consulted for specific recommendations on external component values.

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Freescale Semiconductor, Inc.

For More Information On This Product,

   Go to: www.freescale.com

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