Zilog Z8PE002 Uživatelský manuál stáhnout pdf (Strana 24)

Z8PE002

Z8Plus OTP Microcontroller ZiLOG

24 P R E L I M I N A R Y DS008700-Z8X0799

CLOCK

The Z8Plus MCU derives its timing from on-board clock

circuitry connected to pins

XTAL1 and XTAL2. The clock

circuitry consists of an oscillator, a glitch filter, and a di-

vide-by-two shaping circuit. Figure 12 illustrates the clock

circuitry. The oscillator’s input is

XTAL1 and its output is

XTAL2. The clock can be driven by a crystal, a ceramic res-

onator, LC clock, or an external clock source.

By selecting the

RC OSCILLATOR option in the graphical

user interface (GUI), the circuit may instead be driven by

an external Resistor and Capacitor (

RC) oscillator. Figure

13 illustrates this configuration. This design is limited to no

more than 4 MHz to restrict EMI noise.

Note: The reduced drive strength of this configuration also al-

lows the clock circuit to use a micropower-type crystal

(also known as a tuning fork) without reduction resis-

tors.

Figure 12. Clock Circuit

÷2

XTAL2

XTAL1

Glitch

Filter

÷4

÷8

WDT

Clock

Timer

Clock (TCLK)

Machine

Clock (SCLK)

(5 cycles

per in-

struction)

Figure 13. Z8Plus in RC Oscillator Mode

Glitch

Filter

XTAL2

XTAL1

Note:

4 MHz max.

÷2

V Pin

1 2 ... 19 20 21 22 23 24 25 26 27 28 29 ... 47 48

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