AT90S8515_01 Datasheet, PDF (87/112 Pages) ATMEL Corporation – 8-bit Microcontroller with 8K Bytes In-System Programmable Flash

Data Polling EEPROM
Data Polling Flash
AT90S8515
ing the third byte of the Programming Enable instruction. Whether the echo is
correct or not, all four bytes of the instruction must be transmitted. If the $53 did
not echo back, give SCK a positive pulse and issue a new Programming Enable
instruction. If the $53 is not seen within 32 attempts, there is no functional device
connected.
4. If a Chip Erase is performed (must be done to erase the Flash), wait t_{WD_ERASE}
after the instruction, give RESET a positive pulse and start over from step 2. See
Table 34 on page 89 for t_{WD_ERASE} value.
5. The Flash or 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. Use
Data Polling to detect when the next byte in the Flash or EEPROM can be writ-
ten. If polling is not used, wait t_{WD_PROG} before transmitting the next instruction.
See Table 35 on page 89 for t_{WD_PROG} value. In an erased device, no $FFs in the
data file(s) need to be programmed.
6. Any memory location can be verified by using the Read instruction that returns
the content at the selected address at the serial output MISO (PB6) pin.
7. At the end of the programming session, RESET can be set high to commence
normal operation.
8. Power-off sequence (if needed):
Set XTAL1 to “0” (if a crystal is not used).
Set RESET to “1”.
Turn V_CC power off.
When a byte is being programmed into the EEPROM, reading the address location
being programmed will give the value P1 until the auto-erase is finished and then the
value P2. See Table 31 for P1 and P2 values.
At the time the device is ready for a new EEPROM 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 values P1 and P2, so when programming these values, the user will have to wait
for at least the prescribed time t_{WD_PROG} before programming the next byte. See Table
34 for t_{WD_PROG} value. As a chip-erased device contains $FF in all locations, program-
ming of addresses that are meant to contain $FF can be skipped. This does not apply if
the EEPROM is reprogrammed without first chip-erasing the device.
Table 31. Read Back Value during EEPROM Polling
Part
P1
P2
AT90S8515
$80
$7F
When a byte is being programmed into the Flash, reading the address location being
programmed will give the value $7F. 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 $7F, so when programming this value, the
user will have to wait for at least t_{WD_PROG} before programming the next byte. As a chip-
erased device contains $FF in all locations, programming of addresses that are meant
to contain $FF can be skipped.
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0841G–09/01