ATMEGA1284P-MUR Atmel, ATMEGA1284P-MUR Datasheet - Page 22

• Manufacturer Part Number: ATMEGA1284P-MUR
• Description: MCU AVR 128KB FLASH 20MHZ 44VQFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA1284P-MUR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 32
• Program Memory Size: 128KB (64K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 4K x 8
• Ram Size: 16K x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-VQFN Exposed Pad
• For Use With: ATSTK600 - DEV KIT FOR AVR/AVR32
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

7.4
7.4.1
7.4.2
8272A–AVR–01/10
EEPROM Data Memory
EEPROM Read/Write Access
Preventing EEPROM Corruption
T h e A T m e g a 1 6 4 A / 1 6 4 P A / 3 2 4 A / 3 2 4 P A / 6 4 4 A / 6 4 4 P A / 1 2 8 4 / 1 2 8 4 P c o n t a i n s
512B/1K/2K/4K bytes of data EEPROM memory. It is organized 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 follow-
ing, 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 24
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.
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.
164A/164PA/324A/324PA/644A/644PA/1284/1284P
310,
See Section “7.4.2” on page 22.
for details.
page
314, and
CC
is likely to rise or fall slowly on power-up/down. This causes the device for
CC,
page 299
the EEPROM data can be corrupted because the supply voltage is
respectively.
for details on how to avoid problems in these situations.
Table 7-2 on page
CC
reset Protection circuit can
26. A self-timing function,
”Register Description” on
22