Datasheet
29
4235Kâ8051â05/08
AT89C51RD2/ED2
Figure 11-2. Power Fail Detect
When the power is applied, the Power Monitor immediately asserts a reset. Once the internal
supply after the voltage regulator reach a safety level, the power monitor then looks at the XTAL
clock input. The internal reset will remain asserted until the Xtal1 levels are above and below
VIH and VIL. Further more. An internal counter will count 1024 clock periods before the reset is
de-asserted.
If the internal power supply falls below a safety level, a reset is immediately asserted.
.
Vcc
t
Reset
Vcc
VPFDP
VPFDM