ATmega88 datasheet(295/340 Pages) ATMEL

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7530H–AVR–02/09

ATmega48/88/168 Automotive

The Flash is programmed one page at a time. The memory page is loaded one byte at

a time by supplying the 6 LSB of the address and data together with the Load Program

Memory Page instruction. To ensure correct loading of the page, the data low byte must

be loaded before data high byte is applied for a given address. The Program Memory

Page is stored by loading the Write Program Memory Page instruction with the 8 MSB

of the address. If polling is not used, the user must wait at least t

WD_FLASH before issuing

the next page. (See Table 25-16.) Accessing the serial programming interface before

the Flash write operation completes can result in incorrect programming.

The EEPROM array is programmed one byte at a time by supplying the address and

data together with the appropriate Write instruction. An EEPROM memory location is

first automatically erased before new data is written. If polling is not used, the user must

wait at least t

WD_EEPROM before issuing the next byte. (See Table 25-16.) In a chip

erased device, no 0xFFs in the data file(s) need to be programmed.

Any memory location can be verified by using the Read instruction which returns the

content at the selected address at serial output MISO.

At the end of the programming session, RESET can be set high to commence normal

operation.

Power-off sequence (if needed):

Set RESET to “1”.

Turn V

CC power off.

25.8.2

Data Polling Flash

When a page is being programmed into the Flash, reading an address location within the page

being programmed will give the value 0xFF. At the time the device is ready for a new page, the

programmed value will read correctly. This is used to determine when the next page can be writ-

ten. Note that the entire page is written simultaneously and any address within the page can be

used for polling. Data polling of the Flash will not work for the value 0xFF, so when programming

this value, the user will have to wait for at least t

WD_FLASH before programming the next page. As

a chip-erased device contains 0xFF in all locations, programming of addresses that are meant to

contain 0xFF, can be skipped. See Table 25-16 for t

WD_FLASH value.

25.8.3

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 25-16 for t

WD_EEPROM value.

Table 25-16. Minimum Wait Delay Before Writing the Next Flash or EEPROM Location

Symbol

Minimum Wait Delay

tWD_FLASH

4.5 ms

WD_EEPROM

3.6 ms

tWD_ERASE

9.0 ms

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