Datasheet

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 31-14 Minimum Wait Delay Before Writing the Next Flash or
EEPROM Location, VCC = 5V ± 10% on page 398). In a chip erased device, no 0xFFs in the data
file(s) need to be programmed.
6. Any memory location can be verified by using the Read instruction which returns the content at the
selected address at serial output MISO.
7. At the end of the programming session, RESET can be set high to commence normal operation.
8. Power-off sequence (if needed):
– Set RESET to “1”.
– Turn VCC power off.
Note: If other commands that polling (read) are applied before any write operation (FLASH, EEPROM,
Lock bits, Fuses) is completed, may result in incorrect programming.
Related Links
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31.9.2. 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 written. 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 in next
section for t
WD_FLASH
value.
31.9.3. 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 programmed 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 below for t
WD_EEPROM
value.
Table 31-14 Minimum Wait Delay Before Writing the Next Flash or EEPROM Location, VCC = 5V ± 10%
Symbol Minimum Wait Delay
t
WD_FUSE
4.5ms
t
WD_FLASH
4.5ms
t
WD_EEPROM
9ms
t
WD_ERASE
9ms
Atmel ATmega64A [DATASHEET]
Atmel-8160E-ATmega64A_Datasheet_Complete-09/2015
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