Z8FMC16100 Series Flash MCU
Product Specification
25
Power-On Reset
Each device in the Z8FMC16100 Series Flash MCU contains an internal Power-On Reset
(POR) circuit. 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 (VPOR) and has stabilized, the POR Counter is enabled
and counts 50 cycles of the Internal Precision Oscillator. At this point the System Clock is
enabled and the POR Counter counts a total of 16 system clock pulses. The device is held
in the Reset state until this second POR Counter sequence has timed out. After the
Z8FMC16100 Series Flash MCU exits the Power-On Reset state, the eZ8 CPU fetches the
Reset vector. Following Power-On Reset, the PORstatus bit in the Reset Status and Con-
trol Register is set to 1.
Figure 3 illustrates Power-On Reset operation. Refer to the On-Chip Peripheral AC and
DC Electrical Characteristics section on page 265 for the POR threshold voltage
(VPOR).
VCC = 3.3V
VPOR
VVBO
Program Execution
VCC = 0.0V
System Clock
Internal Precision
Oscillator
Oscillator
Startup
Internal RESET
Signal
Option Bit
Counter Delay
System Clock
Counter Delay
Figure 3. Power-On Reset Operation
Voltage Brown-Out Reset
The Z8FMC16100 Series Flash MCU provides low Voltage Brown-Out (VBO) protection.
The VBO circuit senses when the supply voltage drops to an unsafe level (below the VBO
PS024604-1005
P R E L I M I N A R Y
Power-On Reset
ZILOG [ ZILOG, INC. ]
