SPMCK16Z4MPV16 datasheet(111/500 Pages) FREESCALE

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M68HC16 Z SERIES

SYSTEM INTEGRATION MODULE

USER’S MANUAL

5-5

5.3.1 Clock Sources

The state of the clock mode (MODCLK) pin during reset determines the system clock

source. When MODCLK is held high during reset, the clock synthesizer generates a

clock signal from an external reference frequency. The clock synthesizer control reg-

ister (SYNCR) determines operating frequency and mode of operation. When MOD-

CLK is held low during reset, the clock synthesizer is disabled and an external system

clock signal must be driven onto the EXTAL pin.

The input clock, referred to as fref, can be either a crystal or an external clock source.

The output of the clock system is referred to as fsys. Ensure that fref and fsys are within

normal operating limits.

To generate a reference frequency using the crystal oscillator, a reference crystal

must be connected between the EXTAL and XTAL pins. Typically, a 32.768-kHz crys-

tal is used for a slow reference, but the frequency may vary between 25 kHz to 50 kHz.

Figure 5-3 shows a typical circuit.

Figure 5-3 Slow Reference Crystal Circuit

A 4.194-MHz crystal is typically used for a fast reference, but the frequency may vary

between one MHz up to six MHz. Figure 5-4 shows a typical circuit.

Figure 5-4 Fast Reference Crystal Circuit

32 OSCILLATOR

EXTAL

XTAL

10M

330K

22 pF*

VSSI

RESISTANCE AND CAPACITANCE BASED ON A TEST CIRCUIT CONSTRUCTED WITH A DAISHINKU DMX-38 32.768-kHz CRYSTAL.

SPECIFIC COMPONENTS MUST BE BASED ON CRYSTAL TYPE. CONTACT CRYSTAL VENDOR FOR EXACT CIRCUIT.

16 OSCILLATOR 4M

EXTAL

XTAL

Ω

1.5K

Ω

27 PF*

VSSI

RESISTANCE AND CAPACITANCE BASED ON A TEST CIRCUIT CONSTRUCTED WITH A KDS041-18 4.194 MHz CRYSTAL.

SPECIFIC COMPONENTS MUST BE BASED ON CRYSTAL TYPE. CONTACT CRYSTAL VENDOR FOR EXACT CIRCUIT.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

SPMCK16Z4MPV16 Datasheet(PDF) 111 Page - Freescale Semiconductor, Inc

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