ATmega16U4 datasheet(354/408 Pages) ATMEL

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354

7766D–AVR–01/09

ATmega16U4/ATmega32U4

28.6

Parallel Programming

28.6.1

Enter Programming Mode

The following algorithm puts the device in parallel programming mode:

Apply 4.5 - 5.5V between V

CC and GND.

Set RESET to “0” and toggle XTAL1 at least six times.

Set the Prog_enable pins listed in Table 28-8 on page 353 to “0000” and wait at least

100 ns.

Apply 11.5 - 12.5V to RESET. Any activity on Prog_enable pins within 100 ns after

+12V has been applied to RESET, will cause the device to fail entering programming

mode.

Wait at least 50 µs before sending a new command.

28.6.2

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.

28.6.3

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 perfor med before the Flash and/or EEPROM are

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.

Table 28-12. No. of Words in a Page and No. of Pages in the EEPROM

EEPROM Size

Page Size

PCWORD

No. of

Pages

PCPAGE

EEAMSB

1K bytes

8 bytes

EEA[2:0]

128

EEA[9:3]

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