Rainbow Electronics ATtiny26L - Manual (Page 111)

111
ATtiny26(L)
1477B–AVR–04/02
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.
2. Set RESET to “0” and toggle XTAL1 at least 6 times.
3. Set the Prog_enable pins listed in Table 52 on page 109 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 qual-
ified XTAL1 pulses. In such cases, the following algorithm should be followed:
1. Set Prog_enable pins listed in Table 52 on page 109 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.
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 changed. A Chip Erase must be performed before the Flash is reprogrammed.
Note: 1. The EEPROM memory is preserved during Chip Erase if the EESAVE Fuse is
programmed.
Load Command “Chip Erase”
1. Set XA1, XA0 to “10”. This enables command loading.
2. Set BS1 to “0”.
3. Set DATA to “1000 0000”. This is the command for Chip Erase.
4. Give XTAL1 a positive pulse. This loads the command.
5. Give WR a negative pulse. This starts the Chip Erase. RDY/BSY goes low.
6. Wait until RDY/BSY goes high before loading a new command.