ATmega8A Atmel Corporation, ATmega8A Datasheet - Page 22

• Manufacturer Part Number: ATmega8A
• Manufacturer: Atmel Corporation

Specifications of ATmega8A

• Flash (kbytes): 8 Kbytes
• Pin Count: 32
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 12
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 23
• Ext Interrupts: 2
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Uart: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 1
• Eeprom (bytes): 512
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 3
• Pwm Channels: 3
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

7.6.4
7.6.5
8159D–AVR–02/11
EEPROM Write during Power-down Sleep Mode
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.
When entering Power-down sleep mode while an EEPROM write operation is active, the
EEPROM write operation will continue, and will complete before the Write Access time has
passed. However, when the write operation is completed, the Oscillator continues running, and
as a consequence, the device does not enter Power-down entirely. It is therefore recommended
to verify that the EEPROM write operation is completed before entering Power-down.
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-
ond, 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:
Assembly Code Example
C Code Example
EEPROM_read:
unsigned char EEPROM_read(unsigned int uiAddress)
{
}
; Wait for completion of previous write
sbic EECR,EEWE
rjmp 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<<EEWE))
/* Set up address register */
EEAR = uiAddress;
/* Start eeprom read by writing EERE */
EECR |= (1<<EERE);
/* Return data from data register */
return EEDR;
;
r16,EEDR
CC,
the EEPROM data can be corrupted because the supply voltage is
ATmega8A
22