Manual

101
AT90S/LS8535
1041H–11/01
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 44 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 45 for t
WD_PROG
value. In an erased device, no $FFs in the data file(s)
needs 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.
Data Polling EEPROM 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 41 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
45 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.
Data Polling Flash When a byte is being programmed into the Flash, 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, 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.
Figure 72. Serial Programming Waveforms
Table 41. Read Back Value during EEPROM Polling
Part P1 P2
AT90S/LS8535 $00 $FF
MSB
MSB
LSB
LSB
SERIAL CLOCK INPUT
PB7(SCK)
SERIAL DATA INPUT
PB5(MOSI)
SERIAL DATA OUTPUT
PB6(MISO)