Z8 Encore! XP® F08xA Series
Product Specification
22
VCC = 3.3V
VPOR
VVBO
Program
Execution
VCC = 0.0V
Internal Precision
Oscillator
Crystal
Oscillator
Oscillator
Start-up
Internal RESET
signal
POR
counter delay
optional XTAL
counter delay
Note: Not to Scale
Figure 4.Power-On Reset Operation
Voltage Brown-Out Reset
The devices in the Z8 Encore! XP® F08xA Series provide low Voltage Brown-Out (VBO)
protection. The VBO circuit senses when the supply voltage drops to an unsafe level
(below the VBO threshold voltage) and forces the device into the Reset state. While the
supply voltage remains below the Power-On Reset voltage threshold (VPOR), the VBO
block holds the device in the Reset.
After the supply voltage again exceeds the Power-On Reset voltage threshold, the device
progresses through a full System Reset sequence, as described in the Power-On Reset sec-
tion. Following Power-On Reset, the POR status bit in the Reset Status (RSTSTAT) regis-
ter is set to 1. Figure 5 illustrates Voltage Brown-Out operation. Refer to the chapter
“Electrical Characteristics” on page 191 for the VBO and POR threshold voltages (VVBO
and VPOR).
The Voltage Brown-Out circuit can be either enabled or disabled during STOP mode.
Operation during STOP mode is set by the VBO_AO Flash Option Bit. Refer to the Flash
Option Bits chapter for information about configuring VBO_AO.
PS024705-0405
P R E L I M I N A R Y
Reset and STOP Mode Recovery
ZILOG [ ZILOG, INC. ]
