AT89LP51 Atmel Corporation, AT89LP51 Datasheet - Page 30

• Manufacturer Part Number: AT89LP51
• Manufacturer: Atmel Corporation

Specifications of AT89LP51

• Flash (kbytes): 4 Kbytes
• Max. Operating Frequency: 20 MHz
• Cpu: 8051-1C
• Max I/o Pins: 36
• Uart: 1
• Sram (kbytes): 0.25
• Eeprom (bytes): 256
• Self Program Memory: IAP
• Operating Voltage (vcc): 2.4 to 5.5
• Timers: 3
• Isp: SPI
• Watchdog: Yes

6.2
6.3
30
External Clock Source
Internal RC Oscillator
AT89LP51/52
An optional 5 MΩ on-chip resistor can be connected between XTAL1 and GND. This resistor can
improve the startup characteristics of the oscillator especially at higher frequencies. The resistor
can be enabled/disabled with the R1 User Fuse
Figure 6-2.
Note:
The external clock option disables the oscillator amplifier and allows XTAL1 to be driven directly
by an external clock source as shown in
general purpose I/O P4.7, or configured to output a divided version of the system clock.
Figure 6-3.
The AT89LP51/52 has an Internal Auxiliary oscillator tuned to 1.8432 MHz ±2.0%. When
enabled as the clock source, XTAL1 and XTAL2 may be used as P4.6 and P4.7 respectively.
1. C1, C2 = 5 pF ± 5pF for Crystals
Crystal Oscillator Connections
External Clock Drive Configuration
= 5 pF ± 5pF for Ceramic Resonators
C2
C1
OSCILLA T OR
EXTERNAL
NC GPIO
SIGNAL
Figure
(See “User Configuration Fuses” on page
6-3. XTAL2 may be left unconnected, used as
~10 pF
~10 pF
XT AL2 (P4.7)
XT AL1 (P4.6)
GND
R1
~5 MΩ
3709D–MICRO–12/11
86.)