AT89C51RC Atmel Corporation, AT89C51RC Datasheet - Page 20

• Manufacturer Part Number: AT89C51RC
• Manufacturer: Atmel Corporation

Specifications of AT89C51RC

• Flash (kbytes): 32 Kbytes
• Max. Operating Frequency: 24 MHz
• Cpu: 8051-12C
• Max I/o Pins: 32
• Uart: 1
• Sram (kbytes): 0.5
• Operating Voltage (vcc): 4.0 to 6.0
• Timers: 3
• Watchdog: Yes

19. Power-down Mode
20
AT89C51RC
In the Power-down mode, the oscillator is stopped, and the instruction that invokes Power-down
is the last instruction executed. The on-chip RAM and Special Function Registers retain their
values until the Power-down mode is terminated. Exit from Power-down can be initiated either
by a hardware reset or by an enabled external interrupt. Reset redefines the SFRs but does not
change the on-chip RAM. The reset should not be activated before V
operating level and must be held active long enough to allow the oscillator to restart and
stabilize.
Figure 19-1. Oscillator Connections
Note:
Figure 19-2. External Clock Drive Configuration
Table 19-1.
Mode
Idle
Idle
Power-down
Power-down
C1, C2 = 30 pF ± 10 pF for Crystals
Status of External Pins During Idle and Power-down Modes
Program
Memory
Internal
External
Internal
External
= 40 pF ± 10 pF for Ceramic Resonators
ALE
1
1
0
0
OSCILLATOR
EXTERNAL
SIGNAL
NC
PSEN
C2
C1
1
1
0
0
PORT0
Float
Float
Data
Data
XTAL2
XTAL1
GND
XTAL2
XTAL1
GND
PORT1
Data
Data
Data
Data
Address
PORT2
CC
Data
Data
Data
is restored to its normal
PORT3
Data
Data
Data
Data
1920D–MICRO–6/08