ATmega32U2 datasheet(253/314 Pages) ATMEL

253 / 314 page

253

7799B–AVR–07/09

ATmega8U2/16U2/32U2

Wait until RDY/BSY goes high before loading a new command.

25.7.4

Programming the Flash

The Flash is organized in pages, see Table 25-7 on page 249. When programming the Flash,

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”

Set XA1, XA0 to “10”. This enables command loading.

Set BS1 to “0”.

Set DATA to “0001 0000”. This is the command for Write Flash.

Give XTAL1 a positive pulse. This loads the command.

B. Load Address Low byte (Address bits 7..0)

Set XA1, XA0 to “00”. This enables address loading.

Set BS2, BS1 to “00”. This selects the address low byte.

Set DATA = Address low byte (0x00 - 0xFF).

Give XTAL1 a positive pulse. This loads the address low byte.

C. Load Data Low Byte

Set XA1, XA0 to “01”. This enables data loading.

Set DATA = Data low byte (0x00 - 0xFF).

Give XTAL1 a positive pulse. This loads the data byte.

D. Load Data High Byte

Set BS1 to “1”. This selects high data byte.

Set XA1, XA0 to “01”. This enables data loading.

Set DATA = Data high byte (0x00 - 0xFF).

Give XTAL1 a positive pulse. This loads the data byte.

E. Latch Data

Set BS1 to “1”. This selects high data byte.

Give PAGEL a positive pulse. This latches the data bytes. (See Figure 25-3 for signal

waveforms)

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 Figure 25-2 on page 254. Note that if less than

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 (Address bits15..8)

Set XA1, XA0 to “00”. This enables address loading.

Set BS2, BS1 to “01”. This selects the address high byte.

Set DATA = Address high byte (0x00 - 0xFF).

Give XTAL1 a positive pulse. This loads the address high byte.

H. Load Address Extended High byte (Address bits 23..16)

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