Datasheet

276
8023F–AVR–07/09
ATmega325P/3250P
25.6 Parallel Programming
25.6.1 Enter Programming Mode
The following algorithm puts the device in Parallel (High-voltage) Programming mode:
1. Set Prog_enable pins listed in Table 25-8 on page 275 to “0000”, RESET pin and V
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 µs.
4. Wait 20 - 60 µs, and apply 11.5 - 12.5V to RESET.
Table 25-9. XA1 and XA0 Coding
XA1 XA0 Action when XTAL1 is Pulsed
0 0 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 1 No Action, Idle
Table 25-10. 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
Table 25-11. No. of Words in a Page and No. of Pages in the Flash
Flash Size Page Size PCWORD No. of Pages PCPAGE PCMSB
16K words
(32K bytes)
64 words PC[5:0] 256 PC[13:6] 13
Table 25-12. No. of Words in a Page and No. of Pages in the EEPROM
EEPROM Size Page Size PCWORD No. of Pages PCPAGE EEAMSB
1K bytes 4 bytes EEA[1:0] 256 EEA[13:2] 13