Datasheet
185
ATmega323(L)
1457E–11/01
3. Set DATA to “1000 0000”. This is the command for Chip Erase.
4. Give WR a negative pulse. This starts the Chip Erase. RDY/BSY goes low.
5. Wait until RDY/BSY goes high before loading a new command.
Programming the Flash The Flash is organized as 256 pages of 128 bytes each. When programming the Flash,
the program data is latched into a page buffer. This allows one page of program data to
be programmed 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 ($00 - $FF).
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 ($00 - $FF).
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 ($00 - $FF).
4. Give XTAL1 a positive pulse. This loads the data byte.
E. Latch Data High and Low Byte
1. Set BS1 to “1”.
2. Give PAGEL a positive pulse. See Figure 94 for signal waveforms.
F. Repeat B through F 64 Times to Fill the Page Buffer.
To address a page in the Flash, 8 bits are needed (256 pages). The 6 most significant
bits are read from address high byte as described in section “H” below. The two least
significant page address bits however, are the two most significant bits (bit7 and bit6) of
the latest loaded address low byte as described in section “B”.
G. Load Address High Byte
1. 1. Set XA1, XA0 to “00”. This enables address loading.
2. Set BS1 to “1”. This selects high address.
3. Set DATA = Address high byte ($00 - $3F).
4. Give XTAL1 a positive pulse. This loads the address high byte.