271
Atmel ATmega16/32/64/M1/C1 [DATASHEET]
7647K–AVR–12/13
4.
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 tWD_FLASH before issuing the next page. (See Table 25-16.) Accessing the serial pro- gramming interface before the flash write operation completes can result in incorrect programming.
5.
The EEPROM array is programmed one byte at a time by supplying the address and data together with the appropri-
ate 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 tWD_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.
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.
25.9.2 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 tWD_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 tWD_FLASH value. 25.9.3 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 re-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 tWD_EEPROM before programming the next byte. See
Figure 25-11. Serial Programming Waveforms
Table 25-16. Minimum Wait Delay Before Writing the Next Flash or EEPROM Location
Symbol
Minimum Wait Delay
tWD_FLASH
4.5ms
tWD_EEPROM
3.6ms
tWD_ERASE
9.0ms
Serial data input
(MOSI)
Serial data output
(MISO)
Serial clock input
(SCK)
Sample
MSB
LSB
MSB
LSB