ATmega32A datasheet(271/352 Pages) ATMEL

271 / 352 page

271

8155B–AVR–07/09

ATmega32A

26.7

Parallel Programming

26.7.1

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 26-8 on page 270 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 26-8 on page 270 to “0000”.

Apply 4.5 - 5.5V between V

CC and GND simultanously 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.

26.7.2

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 $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.

26.7.3

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

0000 1000

Read Signature Bytes and Calibration byte

0000 0100

Read Fuse and Lock bits

0000 0010

Read Flash

0000 0011

Read EEPROM

Table 26-10. Command Byte Bit Coding

Command Byte

Command Executed

ATmega32A Datasheet(PDF) 271 Page - ATMEL Corporation

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