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269
8154B–AVR–07/09
ATmega16A
26.7
Parallel Programming
26.7.1
Enter Programming Mode
The following algorithm puts the device in Parallel Programming mode:
1.
Apply 4.5 - 5.5V between V
CC and GND, and wait at least 100 s.
2.
Set RESET to “0” and toggle XTAL1 at least 6 times
3.
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.
2.
Apply 4.5 - 5.5V between V
CC and GND simultaneously as 11.5 - 12.5V is applied to
RESET.
3.
Wait 100 s.
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.
26.7.2
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 $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.
26.7.3
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
0000 1000
Read Signature Bytes and Calibration byte
0000 0100
Read Fuse and Lock bits
0000 0010
Read Flash
0000 0011
Read EEPROM
Table 26-10. Command Byte Bit Coding
Command Byte
Command Executed