112
ATtiny26(L)
1477G–AVR–03/05
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 for at least 100 µs.
2.
Set RESET to “0” and toggle XTAL1 at least 6 times.
3.
Set the Prog_enable pins listed in Table 55 on page 110 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 pro-
gramming mode.
Note:
If the RESET pin is disabled by programming the RSTDISBL Fuse, it may not be possible
to follow the proposed algorithm above. The same may apply when External Crystal or
External RC configuration is selected because it is not possible to apply qualified XTAL1
pulses. In such cases, the following algorithm should be followed:
1.
Set Prog_enable pins listed in Table 55 on page 110 to “0000”.
2.
Apply 4.5 - 5.5V between V
CC
and GND simultanously as 11.5 - 12.5V is applied
to RESET.
3.
Wait 100 ns.
4.
Re-program the fuses to ensure that External Clock is selected as clock source
(CKSEL3:0 = 0b0000) and RESET pin is activated (RSTDISBL unprogrammed).
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.
