Z8F021ASH020EC datasheet(49/276 Pages) ZILOG

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PS022815-0206

Low-Power Modes

Z8 Encore! XP® 4K Series

Product Specification

HALT Mode

Executing the eZ8 CPU’s HALT instruction places the device into HALT mode. In HALT

mode, the operating characteristics are:

• Primary oscillator is enabled and continues to operate.

• System clock is enabled and continues to operate.

• eZ8 CPU is stopped.

• Program counter (PC) stops incrementing.

• Watch-Dog Timer’s internal RC oscillator continues to operate.

• If enabled, the Watch-Dog Timer continues to operate.

• All other on-chip peripherals continue to operate, if enabled.

The eZ8 CPU can be brought out of HALT mode by any of the following operations:

• Interrupt

• Watch-Dog Timer time-out (interrupt or reset)

• Power-On reset

• Voltage-Brown out reset

• External RESET pin assertion

To minimize current in HALT mode, all GPIO pins that are configured as inputs must be

driven to one of the supply rails (VCC or GND).

Peripheral-Level Power Control

In addition to the STOP and Halt modes, it is possible to disable each peripheral on each

of the Z8 Encore! XP® 4K Series devices. Disabling a given peripheral minimizes its

power consumption.

Power Control Register Definitions

Power Control Register 0

Each bit of the following registers disables a peripheral block, either by gating its system

clock input or by removing power from the block.

The default state of the low-power operational amplifier (LPO) is OFF. To use the LPO,

clear the LPO bit, turning it ON. Clearing this bit might interfere with normal ADC mea-

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