ATmega16 datasheet(265/357 Pages) ATMEL

265 / 357 page

265

2466S–AVR–05/09

ATmega16(L)

Parallel

Programming

Enter Programming

Mode

The following algorithm puts the device in Parallel Programming mode:

Apply 4.5 - 5.5V between V

CC and GND, and wait at least 100 µs.

Set RESET to “0” and toggle XTAL1 at least 6 times

Set the Prog_enable pins listed in Table 110 on page 263 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.

Note, if External Crystal or External RC configuration is selected, it may not be possible to apply

qualified XTAL1 pulses. In such cases, the following algorithm should be followed:

Set Prog_enable pins listed in Table 110 on page 263 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.

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 $FF, 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.

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 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.

Programming the

Flash

The Flash is organized in pages, see Table 107 on page 262. When programming the Flash, the

program data is latched into a page buffer. This allows one page of program data to be pro-

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