AT89LP51RD2 Atmel Corporation, AT89LP51RD2 Datasheet - Page 45

• Manufacturer Part Number: AT89LP51RD2
• Manufacturer: Atmel Corporation

Specifications of AT89LP51RD2

• Flash (kbytes): 64 Kbytes
• Max. Operating Frequency: 20 MHz
• Cpu: 8051-1C
• Max I/o Pins: 42
• Spi: 1
• Twi (i2c): 1
• Uart: 1
• Adc Channels: 7
• Adc Resolution (bits): 10
• Adc Speed (ksps): 153.8
• Sram (kbytes): 2.25
• Self Program Memory: API
• Operating Voltage (vcc): 2.4 to 5.5
• Timers: 4
• Isp: SPI/OCD/UART
• Watchdog: Yes

6.2
6.3
6.4
3714A–MICRO–7/11
External Clock Source A
Internal RC Oscillator
Crystal Oscillator B (AT89LP51ID2)
The external clock option disables the oscillator amplifier and allows XTAL1A to be driven
directly by an external clock source as shown in
used as general purpose I/O P4.7, or configured to output a divided version of the system clock.
Figure 6-4.
The AT89LP51RD2/ED2/ID2 has an Internal RC oscillator tuned to 8.0 MHz ±2.5%. When
enabled as clock source A, XTAL1A and XTAL2A may be used as P4.6 and P4.7 respectively.
For AT89LP51ID2 the internal oscillator can also be selected for clock source B, freeing up
XTAL1B and XTAL2B to act as P1.0 and P4.2 respectively. The frequency of the oscillator may
be adjusted within limits by changing the RC Calibration Byte stored at byte 384 of the User Sig-
nature Array. This location may be updated using the IAP interface or by an external device
programmer (User Signature location 0180H). See
page
(0008H in SIG space).
AT89LP51ID2 includes a second crystal oscillator for low-frequency (~32 KHz) operation. When
enabled, internal inverting oscillator amplifier B is connected between XTAL1B and XTAL2B for
connection to an external quartz crystal or ceramic resonator as shown in
in some cases, external capacitors C1 and C2 may be reduced due to the on-chip capacitance
of the XTAL1B and XTAL2B inputs (approximately 10 pF each). An on-chip series resistance is
included between the amplifier and the XTAL2B pad to limit the drive level. In most cases an
external series resistor is not required. When using the crystal oscillator, P1.0 and P4.2 will have
their inputs and outputs disabled. Also, XTAL2B in crystal oscillator mode should not be used to
directly drive a board-level clock without a buffer.
Please note that the low-frequency oscillator may have a very long settling time. The system
must ensure that the oscillator has sufficient time to stabilize before the device is allowed to
operate from this clock source.
190. A copy of the factory calibration byte is stored at byte 8 of the Atmel Signature Array
External Clock A Drive Configuration
AT89LP51RD2/ED2/ID2 Preliminary
OSCILLA T OR
EXTERNAL
NC GPIO
SIGNAL
Figure
Section 24.1.2 “Atmel Signature Array” on
XT AL2A (P4.7)
XT AL1A (P4.6)
GND
6-4. XTAL2A may be left unconnected,
Figure
6-5. Note that
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