ATMEGA162 datasheet(20/325 Pages) ATMEL

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ATmega162/V

2513I–AVR–02/07

EEPROM Data Memory

The ATmega162 contains 512 bytes of data EEPROM memory. It is organized as a sep-

arate 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.

“Memory Programming” on page 233 contains a detailed description on EEPROM Pro-

gramming in SPI, JTAG, or Parallel Programming mode.

EEPROM Read/Write Access

The EEPROM Access Registers are accessible in the I/O space.

The write access time for the EEPROM is given in Table 1. A selftiming function, how-

ever, lets the user software detect when the next byte can be written. If the user code

contains instructions that write the EEPROM, some precautions must be taken. In

heavily filtered power supplies, V

CC is likely to rise or fall slowly on Power-up/down. This

causes the device for some period of time to run at a voltage lower than specified as

minimum for the clock frequency used. See “Preventing EEPROM Corruption” on page

24 for details on how to avoid problems in these situations.

In order to prevent unintentional EEPROM writes, a specific write procedure must be fol-

lowed. 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.

The EEPROM Address

• Bits 15..9 – Res: Reserved Bits

These bits are reserved bits in the ATmega162 and will always read as zero.

• Bits 8..0 – EEAR8..0: EEPROM Address

The EEPROM Address Registers – EEARH and EEARL specify the EEPROM address

in the 512 bytes EEPROM space. The EEPROM data bytes are addressed linearly

between 0 and 511. The initial value of EEAR is undefined. A proper value must be writ-

ten before the EEPROM may be accessed.

Bit

151413121110

––––

–––

EEAR8

EEARH

EEAR7

EEAR6

EEAR5

EEAR4

EEAR3

EEAR2

EEAR1

EEAR0

EEARL

7654

321

Read/Write

RRRR

R/W

Initial Value

0000

000

XXX

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