ATMEGA163 ATMEL [ATMEL Corporation], ATMEGA163 Datasheet - Page 64

• Manufacturer Part Number: ATMEGA163
• Description: 8-bit Microcontroller with 16K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Preventing EEPROM
Corruption
64
ATmega163(L)
The user should poll the EEWE bit before starting the read operation. If a write operation
is in progress, it is not possible to set the EERE bit, nor to change the EEAR Register.
The calibrated Oscillator is used to time the EEPROM accesses. Table 24 lists the typi-
cal programming time for EEPROM access from the CPU
Table 24. EEPROM Programming Time.
During periods of low V
age is too low for the CPU and the EEPROM to operate properly. These issues are the
same as for board level systems using the 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. Secondly, the CPU itself can execute instructions incorrectly, if the
supply voltage for executing instructions is too low.
EEPROM data corruption can easily be avoided by following these design recommen-
dations (one is sufficient):
1. Keep the AVR RESET active (low) during periods of insufficient power supply
2. Keep the AVR core in Power-down Sleep Mode during periods of low V
3. Store constants in Flash memory if the ability to change memory contents from
EEPROM write
(from CPU)
voltage. This can be done by enabling the internal Brown-out Detector (BOD) if
the operating voltage matches the detection level. If not, an external low V
Reset Protection circuit can be used. If a Reset occurs while a write operation is
in progress, the write operation will be completed provided that the power supply
is voltage is sufficient.
will prevent the CPU from attempting to decode and execute instructions, effec-
tively protecting the EEPROM Registers from unintentional writes.
software is not required. Flash memory can not be updated by the CPU unless
the boot loader software supports writing to the Flash and the Boot Lock bits are
configured so that writing to the Flash memory from CPU is allowed. See “Boot
Loader Support” on page 134 for details.
Symbol
Number of Calibrated
RC Oscillator Cycles
CC,
the EEPROM data can be corrupted because the supply volt-
2048
Min Programmingn
1.9 ms
Time
Max Programming
3.8 ms
Time
1142E–AVR–02/03
CC
. This
CC