at89c51re2-slsem ATMEL Corporation, at89c51re2-slsem Datasheet - Page 144

• Manufacturer Part Number: at89c51re2-slsem
• Description: At89c51re2 8-bit Flash Microcontroller
• Manufacturer: ATMEL Corporation

Power Monitor
Description
7663B–8051–03/07
The POR/PFD function monitors the internal power-supply of the CPU core memories
and the peripherals, and if needed, suspends their activity when the internal power sup-
ply falls below a safety threshold. This is achieved by applying an internal reset to them.
By generating the Reset the Power Monitor insures a correct start up when
AT89C51RE2 is powered up.
In order to startup and maintain the microcontroller in correct operating mode, V
to be stabilized in the V
nominal amplitude compatible with logic level VIH/VIL.
These parameters are controlled during the three phases: power-up, normal operation
and power going down. See Figure 43.
Figure 43. Power Monitor Block Diagram
Note:
The Voltage regulator generates a regulated internal supply for the CPU core the mem-
ories and the peripherals. Spikes on the external Vcc are smoothed by the voltage
regulator.
RST pin
XTAL1
1. Once XTAL1 High and low levels reach above and below VIH/VIL. a 1024 clock
period delay will extend the reset coming from the Power Fail Detect. If the power
falls below the Power Fail Detect threshold level, the Reset will be applied
immediately.
PCA
Watchdog
Power Fail Detect
Voltage Regulator
Power On Reset
(1)
Hardware
Watchdog
VCC
CC
operating range and the oscillator has to be stabilized with a
Regulated
Supply
Internal Reset
Peripherals
CPU core
Memories
CC
127
has