MEGA128CAN Datasheet, PDF (339/413 Pages) ATMEL Corporation – Microcontroller WITH 128K BYTES OF ISP FLASH AND CAN CONTROLLER

Data Polling Flash
Data Polling EEPROM
AT90CAN128
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 134 for t_{WD_FLASH} value.
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 deter-
mine 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 134 for
t_{WD_EEPROM} value.
Table 134. Minimum Wait Delay Before Writing the Next Flash or EEPROM Location
Symbol
Minimum Wait Delay
t_{WD_FLASH}
t_{WD_EEPROM}
t_{WD_ERASE}
4.5 ms
9.0 ms
9.0 ms
Figure 163. Serial Programming Waveforms
SERIAL DATA INPUT
MSB
LSB
(MOSI-PDI)
SERIAL DATA OUTPUT
MSB
LSB
(MISO-PDO)
SERIAL CLOCK INPUT
(SCK)
Sample
4250E–CAN–12/04
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