AT89LP51ED2-20JU Atmel, AT89LP51ED2-20JU Datasheet - Page 46

• Manufacturer Part Number: AT89LP51ED2-20JU
• Description: 8-bit Microcontrollers - MCU 64KB 20MHz 2.4V-5.5V
• Manufacturer: Atmel

Specifications of AT89LP51ED2-20JU

• Rohs: yes
• Core: 8051
• Processor Series: AT89x
• Data Bus Width: 8 bit
• Maximum Clock Frequency: 20 MHz
• Program Memory Size: 64 KB
• Data Ram Size: 256 B
• On-chip Adc: Yes
• Operating Supply Voltage: 2.4 V to 5.5 V
• Operating Temperature Range: - 40 C to + 85 C
• Package / Case: PLCC-44
• Mounting Style: SMD/SMT
• Data Rom Size: 4 KB
• Interface Type: 2-Wire, SPI, UART
• Number Of Programmable I/os: 36
• Number Of Timers: 3
• Program Memory Type: Flash
• Factory Pack Quantity: 27

6.5
6.6
46
External Clock Source B (AT89LP51ID2)
Dual Oscillator Support (AT89LP51ID2)
AT89LP51RD2/ED2/ID2 Preliminary
Figure 6-5.
Note:
The external clock option of AT89LP51ID2 disables the oscillator amplifier B and allows XTAL1B
to be driven directly by an external clock source as shown in
unconnected or used as general purpose I/O P4.2.
Figure 6-6.
The AT89LP51ID2 has the ability to switch between two different selectable system clock
sources under software control as shown in
Several operating modes are available and programmable by software:
Selection of which oscillator drives the system clock is controlled by the CKS bit in CKSEL. In
order to switch to a different oscillator, that oscillator must be enabled with the OscAEn or Osc-
• OSCA can be a high frequency crystal, external clock or the internal 8 MHz oscillator
• OSCB can be a low frequency crystal, external clock or the internal 8 MHz oscillator
• Switch system clock source from OSCA to OSCB and vice-versa
• Power down OSCA or OSCB to reduce consumption
• Boot from a fast responding, less accurate oscillator and switch later to a more accurate but
slow to stabilize oscillator.
1. C1, C2 = 10–20 pF for Crystals
Crystal Oscillator B Connections
External Clock A Drive Configuration
= 10–20 pF for Ceramic Resonators
OSCILLA T OR
EXTERNAL
NC GPIO
C2
C1
SIGNAL
Figure 6-2 on page
XTAL2B
XTAL1B
XT AL2B (P4.2)
XT AL1B (P1.0)
GND
~10 pF
~10 pF
Rd
Figure
43.
6-6. XTAL2B may be left
3714A–MICRO–7/11