Z8F082ASH020SC Datasheet, PDF(51/244 Page) Zilog, Inc. – Z8 Encore XP-R F08xA Series with eXtended Peripherals

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Z8F082ASH020SC Datasheet, PDF (51/244 Pages) Zilog, Inc. – Z8 Encore XP-R F08xA Series with eXtended Peripherals

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Z8 Encore! XPÂ® F08xA Series

Product Specification

33

Direct LED Drive

The Port C pins provide a current sinked output capable of driving an LED without requir-

ing an external resistor. The output sinks current at programmable levels of 3mA, 7mA,

13mA and 20mA. This mode is enabled through the Alternate Function sub-register AFS1

and is programmable through the LED control registers.

For correct function, the LED anode must be connected to VDD and the cathode to the

GPIO pin.

Using all Port C pins in LED drive mode with maximum current may result in excessive

total current. Refer to the âElectrical Characteristicsâ on page 191 for the maximum total

current for the applicable package.

Shared Reset Pin

On the 20 and 28-pin devices, the Port D0 pin shares function with a bi-directional reset

pin. Unlike all other I/O pins, this pin does not default to GPIO function on power-up.

This pin acts as a bi-directional reset until user software re-configures it. The Port D0 pin

is output-only when in GPIO mode.

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 âOscillator Control Register Definitionsâ on page 163),

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

5V Tolerance

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 even with the pull-ups 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 Register (page 163) such that the external oscillator is selected as the system clock

For 8-pin devices use PA1 instead of PB3.

PS024705-0405

PRELIMINARY

General-Purpose I/O

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