atmega3250v-8auatmega325v-8ai ATMEL Corporation, atmega3250v-8auatmega325v-8ai Datasheet - Page 270

• Manufacturer Part Number: atmega3250v-8auatmega325v-8ai
• Description: Atmega3250 8-bit Microcontroller With In-system Programmable Flash
• Manufacturer: ATMEL Corporation

27.6
27.6.1
27.6.2
27.6.3
270
Parallel Programming
ATmega325/3250/645/6450
Enter Programming Mode
Considerations for Efficient Programming
Chip Erase
The following algorithm puts the device in Parallel (High-voltage) Programming mode:
1. Set Prog_enable pins listed in
2. Apply 4.5 - 5.5V between V
3. Ensure that V
4. Wait 20 - 60 µs, and apply 11.5 - 12.5V to RESET.
5. Keep the Prog_enable pins unchanged for at least 10µs after the High-voltage has been
6. Wait at least 300 µs 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
tive algorithm can be used.
1. Set Prog_enable pins listed in
2. Apply 4.5 - 5.5V between V
3. Monitor V
4. Keep the Prog_enable pins unchanged for at least 10µs after the High-voltage has been
5. Wait until V
6. Exit Programming mode by power the device down or by bringing RESET pin to 0V.
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
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”
0V.
applied to ensure the Prog_enable Signature has been latched.
V
applied to ensure the Prog_enable Signature has been latched.
commands.
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.
CC
1. The EEPRPOM memory is preserved during Chip Erase if the EESAVE Fuse is programmed.
to 0V.
CC
, and as soon as V
CC
CC
reaches at least 1.8V within the next 20 µs.
actually reaches 4.5 -5.5V before giving any parallel programming
CC
is unable to fulfill the requirements listed above, the following alterna-
CC
CC
and GND.
and GND.
Table 27-7 on page 268
CC
Table 27-7 on page 268
reaches 0.9 - 1.1V, apply 11.5 - 12.5V to RESET.
(1)
memories plus Lock bits. The Lock bits are
to “0000”, RESET pin and V
to “0000”, RESET pin to 0V and
2570L–AVR–08/07
CC
to