ATmega640 Atmel Corporation, ATmega640 Datasheet - Page 26
ATmega640
Manufacturer Part Number
ATmega640
Description
Manufacturer
Atmel Corporation
Specifications of ATmega640
Flash (kbytes)
64 Kbytes
Pin Count
100
Max. Operating Frequency
16 MHz
Cpu
8-bit AVR
# Of Touch Channels
16
Hardware Qtouch Acquisition
No
Max I/o Pins
86
Ext Interrupts
32
Usb Speed
No
Usb Interface
No
Spi
5
Twi (i2c)
1
Uart
4
Graphic Lcd
No
Video Decoder
No
Camera Interface
No
Adc Channels
16
Adc Resolution (bits)
10
Adc Speed (ksps)
15
Analog Comparators
1
Resistive Touch Screen
No
Temp. Sensor
No
Crypto Engine
No
Sram (kbytes)
8
Eeprom (bytes)
4096
Self Program Memory
YES
Dram Memory
No
Nand Interface
No
Picopower
No
Temp. Range (deg C)
-40 to 85
I/o Supply Class
1.8 to 5.5
Operating Voltage (vcc)
1.8 to 5.5
Fpu
No
Mpu / Mmu
no / no
Timers
6
Output Compare Channels
16
Input Capture Channels
4
Pwm Channels
15
32khz Rtc
Yes
Calibrated Rc Oscillator
Yes
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Company
Part Number
Manufacturer
Quantity
Price
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Part Number:
ATmega640-16AU
Manufacturer:
OSRAM
Quantity:
12 000
Part Number:
ATmega640-16AU
Manufacturer:
ATMEL/爱特梅尔
Quantity:
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Part Number:
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Manufacturer:
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56
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8.3.2
2549N–AVR–05/11
Preventing EEPROM Corruption
The next code examples show assembly and C functions for reading the EEPROM. The exam-
ples assume that interrupts are controlled so that no interrupts will occur during execution of
these functions.
Note:
During periods of low V
too low for the CPU and the EEPROM to operate properly. These issues are the same as for
board level systems using EEPROM, and the same design solutions should be applied.
An EEPROM data corruption can be caused by two situations when the voltage is too low. First,
a regular write sequence to the EEPROM requires a minimum voltage to operate correctly. Sec-
ondly, the CPU itself can execute instructions incorrectly, if the supply voltage is too low.
EEPROM data corruption can easily be avoided by following this design recommendation:
Keep the AVR RESET active (low) during periods of insufficient power supply voltage. This can
be done by enabling the internal Brown-out Detector (BOD). If the detection level of the internal
BOD does not match the needed detection level, an external low V
be used. If a reset occurs while a write operation is in progress, the write operation will be com-
pleted provided that the power supply voltage is sufficient.
Assembly Code Example
C Code Example
EEPROM_read:
unsigned char EEPROM_read(unsigned int uiAddress)
{
}
; Wait for completion of previous write
sbic EECR,EEPE
rjcmp EEPROM_read
; Set up address (r18:r17) in address register
out EEARH, r18
out EEARL, r17
; Start eeprom read by writing EERE
sbi EECR,EERE
; Read data from Data Register
in
ret
/* Wait for completion of previous write */
while(EECR & (1<<EEPE))
/* Set up address register */
EEAR = uiAddress;
/* Start eeprom read by writing EERE */
EECR |= (1<<EERE);
/* Return data from Data Register */
return EEDR;
1.
;
See “About Code Examples” on page 11.
r16,EEDR
(1)
CC,
(1)
the EEPROM data can be corrupted because the supply voltage is
ATmega640/1280/1281/2560/2561
CC
reset Protection circuit can
26
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