ATMEGA325-16AJ ATMEL [ATMEL Corporation], ATMEGA325-16AJ Datasheet - Page 262

• Manufacturer Part Number: ATMEGA325-16AJ
• Description: 8-bit Microcontroller with In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Parallel Programming
Enter Programming Mode
Considerations for Efficient
Programming
Chip Erase
Programming the Flash
262
ATmega325/3250/645/6450
The following algorithm puts the device in parallel programming mode:
1. Apply 4.5 - 5.5V between V
2. Set RESET to “0” and toggle XTAL1 at least six times.
3. Set the Prog_enable pins listed in Table 113 on page 260 to “0000” and wait at
4. Apply 11.5 - 12.5V to RESET. Any activity on Prog_enable pins within 100 ns
5. Wait at least 50 µs before sending a new command.
The loaded command and address are retained in the device during programming. For
efficient programming, the following should be considered.
•
•
•
The Chip Erase will erase the Flash and EEPROM
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 EEPROM
are reprogrammed.
Note:
Load Command “Chip Erase”
1. Set XA1, XA0 to “10”. This enables command loading.
2. Set BS1 to “0”.
3. Set DATA to “1000 0000”. This is the command for Chip Erase.
4. Give XTAL1 a positive pulse. This loads the command.
5. Give WR a negative pulse. This starts the Chip Erase. RDY/BSY goes low.
6. Wait until RDY/BSY goes high before loading a new command.
The Flash is organized in pages, see Table 116 on page 261. When programming the
Flash, the program data is latched into a page buffer. This allows one page of program
data to be programmed simultaneously. The following procedure describes how to pro-
gram the entire Flash memory:
A. Load Command “Write Flash”
1. Set XA1, XA0 to “10”. This enables command loading.
2. Set BS1 to “0”.
3. Set DATA to “0001 0000”. This is the command for Write Flash.
4. Give XTAL1 a positive pulse. This loads the command.
B. Load Address Low byte
least 100ns.
after +12V has been applied to RESET, will cause the device to fail entering pro-
gramming mode.
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.
1. The EEPRPOM memory is preserved during Chip Erase if the EESAVE Fuse is
programmed.
CC
and GND.
(1)
memories plus Lock bits. The Lock
2570A–AVR–09/04