X5163, X5165 pdf datasheet (CP

These devices combine four popular functions, Power-on
Reset Control, Watchdog Timer, Supply Voltage Supervision,
and Block Lock Protect Serial EEPROM Memory in one
package. This combination lowers system cost, reduces
board space requirements, and increases reliability.
Applying power to the device activates the power-on reset
circuit which holds RESET/RESET active for a period of
time. This allows the power supply and oscillator to stabilize
before the processor can execute code.
The Watchdog Timer provides an independent protection
mechanism for microcontrollers. When the microcontroller
fails to restart a timer within a selectable time out interval, the
device activates the RESET/RESET signal. The user selects
the interval from three preset values. Once selected, the
interval does not change, even after cycling the power.
The device’s low VCC detection circuitry protects the user’s
system from low voltage conditions, resetting the system when
VCC falls below the minimum VCC trip point. RESET/RESET is
asserted until VCC returns to proper operating level and
stabilizes. Five industry standard VTRIP thresholds are
available, however, Intersil’s unique circuits allow the
threshold to be reprogrammed to meet custom requirements
or to fine-tune the threshold for applications requiring higher
precision.