Datasheet

1. Set the Prog_enable pins listed in the table Pin Values Used to Enter Programming Mode above to
“0000”, RESET pin to 0V and V
CC
to 0V.
2. Apply 4.5–5.5V between V
CC
and GND.
3. Monitor V
CC
, and as soon as V
CC
reaches 0.9–1.1V, apply 11.5–12.5V to RESET.
4. Keep the Prog_enable pins unchanged for at least 10 μs after the high voltage has been applied to
ensure the Prog_enable signature has been latched.
5. Wait until V
CC
reaches 4.5–5.5V before giving any parallel programming commands.
6. Exit Programming mode by powering down the device or by bringing RESET pin to 0V.
32.8.2 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.
32.8.3 Chip Erase
The chip erase will erase the Flash, the SRAM and the EEPROM 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 EEPROM are reprogrammed.
Note: The EEPROM memory is preserved during chip erase if the EESAVE fuse is programmed.
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.
32.8.4 Programming the Flash
The Flash is organized in pages as a number of words in a page and number of pages in the Flash.
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 program the
entire Flash memory:
Step 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.
Step B. Load Address Low Byte
1. Set XA1, XA0 to “00”. This enables address loading.
ATmega48PA/88PA/168PA
Memory Programming (MEMPROG)
© 2018 Microchip Technology Inc.
Datasheet Complete
DS40002011A-page 372