Z8F042ASJ020EG2156 Datasheet, PDF (48/280 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F082A Series
Product Specification
32
Low-Power Modes
The Z8 Encore! XP F082A Series products contain power-saving features. The highest
level of power reduction is provided by the Stop Mode, in which nearly all device func-
tions are powered down. The next lower level of power reduction is provided by the Halt
Mode, in which the CPU is powered down.
Further power savings can be implemented by disabling individual peripheral blocks
while in Active mode (defined as being in neither Stop nor Halt Mode).
Stop Mode
Executing the eZ8 CPU’s Stop instruction places the device into Stop Mode, powering
down all peripherals except the Voltage Brown-Out detector, the Low-power Operational
Amplifier and the Watchdog Timer. These three blocks may also be disabled for additional
power savings. Specifically, the operating characteristics are:
• Primary crystal oscillator and internal precision oscillator are stopped; X_IN and X_OUT
(if previously enabled) are disabled and PA0/PA1 revert to the states programmed by
the GPIO registers
• System clock is stopped
• eZ8 CPU is stopped
• Program counter (PC) stops incrementing
• Watchdog Timer’s internal RC oscillator continues to operate if enabled by the Oscil-
lator Control Register
• If enabled, the Watchdog Timer logic continues to operate
• If enabled for operation in Stop Mode by the associated Flash option bit, the Voltage
Brown-Out protection circuit continues to operate
• Low-power operational amplifier continues to operate if enabled by the Power Control
Register
• All other on-chip peripherals are idle
To minimize current in Stop Mode, all GPIO pins that are configured as digital inputs must
be driven to one of the supply rails (V_CC or GND). Additionally, any GPIOs configured as
outputs must also be driven to one of the supply rails. The device can be brought out of
Stop Mode using Stop Mode Recovery. For more information about Stop Mode Recovery,
see the Reset, Stop Mode Recovery and Low Voltage Detection chapter on page 22.
PS022828-0413
PRELIMINARY
Low-Power Modes