AT89LP6440-20AU Atmel, AT89LP6440-20AU Datasheet - Page 30

• Manufacturer Part Number: AT89LP6440-20AU
• Description: MCU 8051 64K FLASH ISP 44TQFP
• Manufacturer: Atmel
• Series: 89LPr

Specifications of AT89LP6440-20AU

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 38
• Program Memory Size: 64KB (64K x 8)
• Program Memory Type: FLASH
• Eeprom Size: 8K x 8
• Ram Size: 4.25K x 8
• Voltage - Supply (vcc/vdd): 2.4 V ~ 3.6 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-TQFP, 44-VQFP
• Package: 44TQFP
• Device Core: 8051
• Family Name: 89LP
• Maximum Speed: 20 MHz
• Operating Supply Voltage: 2.5|3.3 V
• Data Bus Width: 8 Bit
• Number Of Programmable I/os: 38
• Interface Type: 2-Wire/SPI
• On-chip Dac: 8-chx10-bit
• Number Of Timers: 3
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

6. System Clock
6.1
30
Crystal Oscillator
AT89LP6440 - Preliminary
The system clock is generated directly from one of three selectable clock sources. The three
sources are the on-chip crystal oscillator, external clock source, and internal RC oscillator. The
on-chip crystal oscillator may also be configured for low or high speed operation. The clock
source is selected by the Clock Source User Fuses as shown in
tion Fuses” on page
from the system clock. However, the system clock divider may be used to prescale the system
clock. The choice of clock source also affects the start-up time after a POR, BOD or Power-
down event (See
Table 6-1.
When enabled, the internal inverting oscillator amplifier is connected between XTAL1 and
XTAL2 for connection to an external quartz crystal or ceramic resonator. The oscillator may
operate in either high-speed or low-speed mode. Low-speed mode is intended for 32.768 kHz
watch crystals and consumes less power than high-speed mode. The configuration as shown in
Figure 6-1
device adds about 10 pF of capacitance to both XTAL1 and XTAL2, so that in some cases an
external capacitor may NOT be required. It is recommended that a resistor R1 be connected to
XTAL1, instead of load capacitor C1, for improved startup performance. The total capacitance
on XTAL1 or XTAL2, including the external load capacitor plus internal device load, board trace
and crystal loadings, should not exceed 20 pF. When using the crystal oscillator, P4.0 and P4.1
will have their inputs and outputs disabled. Also, XTAL2 in crystal oscillator mode should not be
used to directly drive a board-level clock without a buffer.
Figure 6-1.
Note:
Clock Source
Fuse 1
1. C1
0
0
1
1
applies for both high and low speed oscillators. Note that the internal structure of the
R1
Clock Source Settings
Crystal Oscillator Connections
“Reset” on page 32
= 0–10 pF for Crystals
= 0–10 pF for Ceramic Resonators
= 4–5 MΩ
164. By default, no internal clock division is used to generate the CPU clock
Clock Source
Fuse 0
0
1
0
1
or
C2
R1
“Power-down Mode” on page
Selected Clock Source
High Speed Crystal Oscillator (f > 500 kHz)
Low Speed Crystal Oscillator (f ≤ 100 kHz)
External Clock on XTAL1
Internal 8 MHz RC Oscillator
~10 pF
~10 pF
Table
6-1. See
36)
“User Configura-
3706A–MICRO–9/09