ATmega64A datasheet(301/392 Pages) ATMEL

301 / 392 page

301

8160C–AVR–07/09

ATmega64A

Set Prog_enable pins listed in Table on page 299 to “0000”.

Apply 4.5 - 5.5V between V

CC and GND simultaneously as 11.5 - 12.5V is applied to

RESET.

Wait 100 µs.

Re-program the fuses to ensure that External Clock is selected as clock source

(CKSEL3:0 = 0b0000) If Lock bits are programmed, a Chip Erase command must be

executed before changing the fuses.

Exit Programming mode by power the device down or by bringing RESET pin to 0b0.

Entering Programming mode with the original algorithm, as described above.

27.6.2

Considerations for Efficient Programming

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.

•

Skip writing the data value 0xFF, that is the contents of the entire EEPROM (unless the

EESAVE Fuse is programmed) and Flash after a Chip Erase.

•

Address high byte needs only be loaded before programming or reading a new 256 word

window in Flash or 256 byte EEPROM. This consideration also applies to Signature bytes

reading.

27.6.3

Chip Erase

The Chip Erase will erase the Flash and EEPROM

(1) memories plus Lock bits. The Lock bits are

not reset until the program memory has been completely erased. The Fuse bits are not

changed. A Chip Erase must be performed before the Flash and/or the EEPROM

reprogrammed.

Note:

1. The EEPRPOM memory is preserved during chip erase if the EESAVE Fuse is programmed.

Load Command “Chip Erase”

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

Set BS1 to “0”.

Set DATA to “1000 0000”. This is the command for Chip Erase.

Give XTAL1 a positive pulse. This loads the command.

Give WR a negative pulse. This starts the Chip Erase. RDY/BSY goes low.

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

27.6.4

Programming the Flash

The Flash is organized in pages, see Table 27-9 on page 300. 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.

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