Datasheet

167
8183F–AVR–06/12
ATtiny24A/44A/84A
19.7.1 Enter High-voltage Serial Programming Mode
The following algorithm puts the device in High-voltage Serial Programming mode:
1. Set Prog_enable pins listed in Table 19-14 on page 166 to “000”, RESET pin and V
CC
to 0V.
2. Apply 4.5 - 5.5V between V
CC
and GND. Ensure that V
CC
reaches at least 1.8V within
the next 20 µs.
3. Wait 20 - 60 µs, and apply 11.5 - 12.5V to RESET.
4. Keep the Prog_enable pins unchanged for at least 10 µs after the High-voltage has
been applied to ensure the Prog_enable Signature has been latched.
5. Release the Prog_enable[2] pin after t
HVRST
has elapsed.
6. Wait at least 300 µs before giving any serial instructions on SDI/SII.
7. Exit Programming mode by power the device down or by bringing RESET pin to 0V.
If the rise time of the V
CC
is unable to fulfill the requirements listed above, the following alterna-
tive algorithm can be used:
1. Set Prog_enable pins listed in Table 19-14 on page 166 to “000”, RESET pin and V
CC
to 0V.
2. Apply 4.5 - 5.5V between V
CC
and GND.
3. Monitor V
CC
, and as soon as V
CC
reaches 0.9 - 1.1V, apply 11.5 - 12.5V to RESET.
4. Keep the Prog_enable pins unchanged for at least 10 µs after the High-voltage has
been applied to ensure the Prog_enable Signature has been latched.
5. Release the Prog_enable[2] pin to avoid drive contention on the Prog_enable[2]/SDO
pin.
6. Wait until V
CC
actually reaches 4.5 - 5.5V before giving any serial instructions on
SDI/SII.
7. Exit Programming mode by power the device down or by bringing RESET pin to 0V.
Table 19-15. High-voltage Reset Characteristics
Supply Voltage RESET Pin High-voltage Threshold
Minimum High-voltage Period for
Latching Prog_enable
V
CC
V
HVRST
t
HVRST
4.5V 11.5V 100 ns
5.5V 11.5V 100 ns