ATMEGA644P-A15MZ Atmel, ATMEGA644P-A15MZ Datasheet - Page 21

• Manufacturer Part Number: ATMEGA644P-A15MZ
• Description: MCU AVR 64KB FLASH 16MHZ 44QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA644P-A15MZ

• Package / Case: 44-VQFN Exposed Pad
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Speed: 16MHz
• Number Of I /o: 32
• Eeprom Size: 2K x 8
• Core Processor: AVR
• Program Memory Type: FLASH
• Ram Size: 4K x 8
• Program Memory Size: 64KB (64K x 8)
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Connectivity: I²C, SPI, UART/USART
• Core Size: 8-Bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

6.4
6.4.1
6.4.2
7674F–AVR–09/09
EEPROM Data Memory
EEPROM Read/Write Access
Preventing EEPROM Corruption
The ATmega164P/324P/644P contains 512B/1K/2K bytes of data EEPROM memory. It is orga-
nized as a separate data space, in which single bytes can be read and written. The EEPROM
has an endurance of at least 100,000 write/erase cycles. The access between the EEPROM and
the CPU is described in the following, specifying the EEPROM Address Registers, the EEPROM
Data Register, and the EEPROM Control Register.
For a detailed description of SPI, JTAG and Parallel data downloading to the EEPROM, see
page
The EEPROM Access Registers are accessible in the I/O space. See
page 23
The write access time for the EEPROM is given in
however, lets the user software detect when the next byte can be written. If the user code con-
tains instructions that write the EEPROM, some precautions must be taken. In heavily filtered
power supplies, V
some period of time to run at a voltage lower than specified as minimum for the clock frequency
used.
these situations.
In order to prevent unintentional EEPROM writes, a specific write procedure must be followed.
Refer to the description of the EEPROM Control Register for details on this.
When the EEPROM is read, the CPU is halted for four clock cycles before the next instruction is
executed. When the EEPROM is written, the CPU is halted for two clock cycles before the next
instruction is executed.
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.
311,
See “Preventing EEPROM Corruption” on page 21.
for details.
page
315, and
CC
is likely to rise or fall slowly on power-up/down. This causes the device for
CC,
page 300
the EEPROM data can be corrupted because the supply voltage is
respectively.
ATmega164P/324P/644P
Table 6-2 on page
for details on how to avoid problems in
CC
reset Protection circuit can
25. A self-timing function,
“Register Description” on
21