4. Give XTAL1 a positive pulse. This loads the command.
B: Load Address High Byte
1. Set XA1, XA0 to “00”. This enables address loading.
2. Set BS to “1”. This selects high byte.
3. Set DATA = Address high byte ($00 - $01).
4. Give XTAL1 a positive pulse. This loads the address high byte.
C: Load Address Low Byte
1. Set XA1, XA0 to “00”. This enables address loading.
2. Set BS to “0”. This selects low byte.
3. Set DATA = Address low byte ($00 - $FF).
4. Give XTAL1 a positive pulse. This loads the address low byte.
D: Load Data Low Byte
1. Set XA1, XA0 to “01”. This enables data loading.
2. Set DATA = Data low byte ($00 - $FF).
3. Give XTAL1 a positive pulse. This loads the data low byte.
E: Write Data Low Byte
1. Set BS to “0”. This selects low data.
2. Give WR a negative pulse. This starts programming of the data byte. RDY/BSY
goes low.
3. Wait until RDY/BSY goes high to program the next byte.
(See Figure 31 for signal waveforms.)
F: Load Data High Byte
1. Set XA1, XA0 to “01”. This enables data loading.
2. Set DATA = Data high byte ($00 - $FF).
3. Give XTAL1 a positive pulse. This loads the data high byte.
G: Write Data High Byte
1. Set BS to “1”. This selects high data.
2. Give WR a negative pulse. This starts programming of the data byte. RDY/BSY
goes low.
3. Wait until RDY/BSY goes high to program the next byte.
(See Figure 32 for signal waveforms.)
The loaded command and address are retained in the device during programming. For
efficient programming, the following should be considered:
•
•
•
The command needs only be loaded once when writing or reading multiple memory
locations.
Address high byte needs only be loaded before programming a new 256-word page
in the Flash.
Skip writing the data value $FF; that is, the contents of the entire Flash and
EEPROM after a Chip Erase.
These considerations also apply to EEPROM programming and Flash, EEPROM and
signature byte reading.
40
AT90S1200
0838H–AVR–03/02
ATMEL [ ATMEL ]
