Clock, And its output is – Zilog Z8PE002 User Manual

Page 24

Z8PE002
Z8Plus OTP Microcontroller

ZiLOG

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 (

) 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.

V Pin