z8f1621 ZiLOG Semiconductor, z8f1621 Datasheet - Page 61

• Manufacturer Part Number: z8f1621
• Description: High Performance 8-bit Microcontrollers
• Manufacturer: ZiLOG Semiconductor

PS019921-0308
Internal RESET
WDT Clock
Not to Scale
VCC = 0.0 V
Oscillator
Primary
signal
Power-On Reset
Voltage Brownout Reset
V
V
POR
VBO
Each device in the Z8 Encore! XP F64XX Series contains an internal Power-On Reset cir-
cuit. The POR circuit monitors the supply voltage and holds the device in the Reset state
until the supply voltage reaches a safe operating level. After the supply voltage exceeds
the POR voltage threshold (V
the Watchdog Timer oscillator. After the POR counter times out, the XTAL Counter is
enabled to count a total of 16 system clock pulses. The devices are held in the Reset state
until both the POR Counter and XTAL counter have timed out. After the Z8 Encore! XP
F64XX Series devices exit the Power-On Reset state, the eZ8 CPU fetches the Reset vec-
tor. Following Power-On Reset, the POR status bit in the Watchdog Timer Control
(WDTCTL) register is set to 1.
Figure 7
Electrical Characteristics
The devices in the Z8 Encore! XP F64XX Series provide low Voltage Brownout
protection. The VBO circuit senses when the supply voltage drops to an unsafe level
displays Power-On Reset operation. For the POR threshold voltage (V
Oscillator
Start-up
Figure 7. Power-On Reset Operation
on page 211.
counter delay
POR
POR
), the POR Counter is enabled and counts 66 cycles of
counter delay
XTAL
Z8 Encore! XP
Reset and Stop Mode Recovery
Product Specification
Execution
Program
®
F64XX Series
VCC = 3.3 V
POR
), see
47