AT89C51RD2 Atmel Corporation, AT89C51RD2 Datasheet - Page 28

• Manufacturer Part Number: AT89C51RD2
• Manufacturer: Atmel Corporation

Specifications of AT89C51RD2

• Flash (kbytes): 64 Kbytes
• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 32
• Spi: 1
• Uart: 1
• Sram (kbytes): 2
• Self Program Memory: API
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 4
• Isp: UART
• Watchdog: Yes

11. Power Monitor
11.1
28
Description
AT89C51RD2/ED2
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 supply 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 AT89C51RD2/ED2
is powered up.
In order to startup and maintain the microcontroller in correct operating mode, V
bilized in the V
compatible with logic level VIH/VIL.
These parameters are controlled during the three phases: power-up, normal operation and
power going down. See Figure 11-1.
Figure 11-1. Power Monitor Block Diagram
Note:
The Voltage regulator generates a regulated internal supply for the CPU core the memories and
the peripherals. Spikes on the external Vcc are smoothed by the voltage regulator.
The Power fail detect monitor the supply generated by the voltage regulator and generate a
reset if this supply falls below a safety threshold as illustrated in the Figure 11-2 below.
RST pin
1. Once XTAL1 High and low levels reach above and below VIH/VIL. a 1024 clock period delay
XTAL1
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.
CC
PCA
Watchdog
operating range and the oscillator has to be stabilized with a nominal amplitude
Voltage Regulator
Power Fail Detect
Power On Reset
(1)
Hardware
Watchdog
VCC
Regulated
Supply
Internal Reset
Peripherals
CPU core
Memories
CC
4235K–8051–05/08
has to be sta-