ATmega64A datasheet(312/392 Pages) ATMEL

312 / 392 page

312

8160C–AVR–07/09

ATmega64A

27.8.3

Data Polling EEPROM

When a new byte has been written and is being programmed into EEPROM, reading the

address location being programmed will give the value 0xFF. At the time the device is ready for

a new byte, the programmed value will read correctly. This is used to determine when the next

byte can be written. This will not work for the value 0xFF, but the user should have the following

in mind: As a chip erased device contains 0xFF in all locations, programming of addresses that

are meant to contain 0xFF, can be skipped. This does not apply if the EEPROM is re-pro-

grammed without chip erasing the device. In this case, data polling cannot be used for the value

0xFF, and the user will have to wait at least t

WD_EEPROM before programming the next byte. See

Table 27-14 for t

WD_EEPROM value.

Note:

1. Flash write: per page

Figure 27-11. SPI Serial Programming Waveforms

Table 27-14. Minimum Wait Delay before Writing the Next Flash or EEPROM Location

Symbol

Minimum Wait Delay

tWD_FUSE

4.5 ms

tWD_FLASH

(1)

4.5 ms

WD_EEPROM

9.0 ms

tWD_ERASE

9.0 ms

MSB

LSB

SERIAL CLOCK INPUT

(SCK)

SERIAL DATA INPUT

(MOSI)

(MISO)

SAMPLE

SERIAL DATA OUTPUT

ATmega64A Datasheet(PDF) 312 Page - ATMEL Corporation