atmega3250v-8auatmega325v-8ai ATMEL Corporation, atmega3250v-8auatmega325v-8ai Datasheet - Page 271

• Manufacturer Part Number: atmega3250v-8auatmega325v-8ai
• Description: Atmega3250 8-bit Microcontroller With In-system Programmable Flash
• Manufacturer: ATMEL Corporation

27.6.4
2570L–AVR–08/07
Programming the Flash
1. Set XA1, XA0 to “10”. This enables command loading.
2. Set BS1 to “0”.
3. Set DATA to “1000 0000”. This is the command for Chip Erase.
4. Give XTAL1 a positive pulse. This loads the command.
5. Give WR a negative pulse. This starts the Chip Erase. RDY/BSY goes low.
6. Wait until RDY/BSY goes high before loading a new command.
The Flash is organized in pages, see
the program data is latched into a page buffer. This allows one page of program data to be pro-
grammed simultaneously. The following procedure describes how to program the entire Flash
memory:
A. Load Command “Write Flash”
1. Set XA1, XA0 to “10”. This enables command loading.
2. Set BS1 to “0”.
3. Set DATA to “0001 0000”. This is the command for Write Flash.
4. Give XTAL1 a positive pulse. This loads the command.
B. Load Address Low byte
1. Set XA1, XA0 to “00”. This enables address loading.
2. Set BS1 to “0”. This selects low address.
3. Set DATA = Address low byte (0x00 - 0xFF).
4. Give XTAL1 a positive pulse. This loads the address low byte.
C. Load Data Low Byte
1. Set XA1, XA0 to “01”. This enables data loading.
2. Set DATA = Data low byte (0x00 - 0xFF).
3. Give XTAL1 a positive pulse. This loads the data byte.
D. Load Data High Byte
1. Set BS1 to “1”. This selects high data byte.
2. Set XA1, XA0 to “01”. This enables data loading.
3. Set DATA = Data high byte (0x00 - 0xFF).
4. Give XTAL1 a positive pulse. This loads the data byte.
E. Latch Data
1. Set BS1 to “1”. This selects high data byte.
2. Give PAGEL a positive pulse. This latches the data bytes. (See
F. Repeat B through E until the entire buffer is filled or until all data within the page is loaded.
While the lower bits in the address are mapped to words within the page, the higher bits address
the pages within the FLASH. This is illustrated in
eight bits are required to address words in the page (pagesize < 256), the most significant bit(s)
in the address low byte are used to address the page when performing a Page Write.
G. Load Address High byte
waveforms)
Table 27-10 on page
ATmega325/3250/645/6450
Figure 27-2 on page
269. When programming the Flash,
272. Note that if less than
Figure 27-3
for signal
271