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ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P [DATASHEET]
8285E–AVR–02/2013
27.7
Parallel programming
27.7.1
Enter programming mode
The following algorithm puts the device in parallel programming mode:
1.
Apply 4.5 - 5.5V between V
CC and GND.
2.
Set RESET to “0” and toggle XTAL1 at least six times.
3.
4.
Apply 11.5 - 12.5V to RESET. Any activity on Prog_enable pins within 100ns after +12V has been applied to
RESET, will cause the device to fail entering programming mode.
5.
Wait at least 50s before sending a new command.
27.7.2
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 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.
Table 27-11. XA1 and XA0 coding.
XA1
XA0
Action when XTAL1 is pulsed
00
Load Flash or EEPROM Address (High or low address byte determined by
BS1).
0
1
Load Data (High or Low data byte for Flash determined by BS1).
1
0
Load Command
1
No Action, Idle
Table 27-12. Command Byte bit coding.
Command byte
Command executed
1000 0000
Chip Erase
0100 0000
Write Fuse bits
0010 0000
Write Lock bits
0001 0000
Write Flash
0001 0001
Write EEPROM
0000 1000
Read Signature Bytes and Calibration byte
0000 0100
Read Fuse and Lock bits
0000 0010
Read Flash
0000 0011
Read EEPROM