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2467S–AVR–07/09
ATmega128
Parallel
Programming
Enter Programming
Mode
The following algorithm puts the device in parallel programming mode:
1.
Apply 4.5 - 5.5 V between V
CC
and GND, and wait at least 100 µs.
2.
Set RESET to “0” and toggle XTAL1 at least SIX times.
3.
Set the Prog_enable pins listed in
to “0000” and wait at least 100
ns.
4.
Apply 11.5 - 12.5V to RESET. Any activity on Prog_enable pins within 100 ns after +12V
has been applied to RESET, will cause the device to fail entering programming mode.
Note, if External Crystal or External RC configuration is selected, it may not be possible to apply
qualified XTAL1 pulses. In such cases, the following algorithm should be followed:
1.
Set Prog_enable pins listed in
to “0000”.
2.
Apply 4.5 - 5.5V between V
CC
and GND simultaneously as 11.5 - 12.5V is applied to
RESET.
3.
Wait 100 µs.
4.
Re-program the fuses to ensure that External Clock is selected as clock source
(CKSEL3:0 = 0b0000) If Lock bits are programmed, a Chip Erase command must be
executed before changing the fuses.
5.
Exit Programming mode by power the device down or by bringing RESET pin to 0b0.
6.
Entering Programming mode with the original algorithm, as described above.
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 $FF, 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.
Chip Erase
The Chip Erase will erase the Flash and 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 the EEPROM are
reprogrammed.
Note:
1. The EEPRPOM memory is preserved during chip erase if the EESAVE fuse is programmed.
Table 124.
No. of Words in a Page and no. of Pages in the Flash
Flash Size
Page Size
PCWORD
No. of Pages
PCPAGE
PCMSB
64K words (128K bytes)
128 words
PC[6:0]
512
PC[15:7]
15
Table 125.
No. of Words in a Page and no. of Pages in the EEPROM
EEPROM Size
Page Size
PCWORD
No. of Pages
PCPAGE
EEAMSB
4K bytes
8 bytes
EEA[2:0]
512
EEA[11:3]
8
