299
2552K–AVR–04/11
ATmega329/3290/649/6490
27.6
Parallel Programming
27.6.1
Enter Programming Mode
The following algorithm puts the device in Parallel (High-voltage) Programming mode:
1.
CC to
0V.
2.
Apply 4.5 - 5.5V between V
CC and GND.
3.
Ensure that V
CC reaches at least 1.8V within the next 20 s.
4.
Wait 20 - 60 s, and apply 11.5 - 12.5V to RESET.
5.
Keep the Prog_enable pins unchanged for at least 10s after the High-voltage has been
applied to ensure the Prog_enable Signature has been latched.
6.
Wait at least 300 s before giving any parallel programming commands.
7.
Exit Programming mode by power the device down or by bringing RESET pin to 0V.
If the rise time of the V
CC is unable to fulfill the requirements listed above, the following alterna-
tive algorithm can be used.
1.
V
CC to 0V.
2.
Apply 4.5 - 5.5V between V
CC and GND.
3.
Monitor V
CC, and as soon as VCC reaches 0.9 - 1.1V, apply 11.5 - 12.5V to RESET.
4.
Keep the Prog_enable pins unchanged for at least 10s after the High-voltage has been
applied to ensure the Prog_enable Signature has been latched.
5.
Wait until V
CC actually reaches 4.5 -5.5V before giving any parallel programming
commands.
6.
Exit Programming mode by power the device down or by bringing RESET pin to 0V.
27.6.2
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.
27.6.3
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”