Datasheet

257
ATmega48/88/168 Automotive [DATASHEET]
7530K–AVR–07/14
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 8MSB 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.
5. 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.
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 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 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 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-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 25-16 for t
WD_EEPROM
value.
Figure 25-11.Serial Programming Waveforms
Table 25-16. Minimum Wait Delay Before Writing the Next Flash or EEPROM Location
Symbol Minimum Wait Delay
t
WD_FLASH
4.5ms
t
WD_EEPROM
3.6ms
t
WD_ERASE
9.0ms
SERIAL DATA INPUT
(MOSI)
SERIAL DATA OUTPUT
(MISO)
SERIAL CLOCK INPUT
(SCK)
SAMPLE
MSB LSB
MSB LSB