Z8 Encore! XP® 4K Series
Product Specification
35
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
Note:
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.
PS022815-0206
General-Purpose I/O
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