Z8F021ASH020SC datasheet(54/276 Pages) ZILOG

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PS022815-0206

General-Purpose I/O

Z8 Encore! XP® 4K Series

Product Specification

Crystal Oscillator Override

For systems using a crystal oscillator, PA0 and PA1 are used to connect the crystal. When

the crystal oscillator is enabled (see Oscillator Control Register Definitions on page 183),

the GPIO settings are overridden and PA0 and PA1 are disabled.

5V Tolerance

All six I/O pins on the 8-pin devices are 5V-tolerant, unless the programmable pull-ups are

enabled. If the pull-ups are enabled and inputs higher than VDD are applied to these parts,

excessive current flows through those pull-up devices and can damage the chip.

In the 20- and 28-pin versions of this device, any pin which shares functionality with an

ADC, crystal or comparator port is not 5V-tolerant, including PA[1:0], PB[5:0] and

PC[2:0]. All other signal pins are 5V-tolerant, and can safely handle inputs higher than

VDD except when the programmable pull-ups are enabled.

External Clock Setup

For systems using an external TTL drive, PB3 is the clock source for 20- and 28-pin

devices. In this case, configure PB3 for alternate function CLKIN. Write the Oscillator

Control (OSCCTL)Register (page 183) such that the external oscillator is selected as the

system clock. For 8-pin devices use PA1 instead of PB3.

Note:

Z8F021ASH020SC 数据表(PDF) 54 Page - Zilog, Inc.