306
8151H–AVR–02/11
ATmega128A
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 $FF in all locations, programming of addresses that are meant to
WD_FLASH value
26.8.3
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 $FF. 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 $FF, but the user should have the following in
mind: As a chip-erased device contains $FF in all locations, programming of addresses that are
meant to contain $FF, 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 $FF, and
the user will have to wait at least t
WD_EEPROM before programming the next byte. See Table 26-14 for t
WD_EEPROM value.
Figure 26-8. .SPI Serial Programming Waveforms
Table 26-14. Minimum Wait Delay before Writing the Next Flash or EEPROM Location, V
CC =
5V ±10%
Symbol
Minimum Wait Delay
t
WD_FUSE
4.5ms
tWD_FLASH
5ms
tWD_EEPROM
10ms
t
WD_ERASE
10ms
MSB
LSB
SERIAL CLOCK INPUT
(SCK)
SERIAL DATA INPUT
(MOSI)
(MISO)
SAMPLE
SERIAL DATA OUTPUT