I am working up a project that has a built in ATTiny fuse reset function, and have a question on the HVSP as per Atmel's information...
1. Set Prog_enable pins (SDI, SII, SDO, SCI) “0”, RESET pin and VCC to 0V.
2. Apply 5V between VCC and GND. Ensure that VCC reaches at least 1.8V within the next 20 microseconds.
3. Wait 20 - 60 us, and apply 11.5 - 12.5V to RESET.
4. Keep the Prog_enable pins unchanged for at least 10 us after the High-voltage has been
applied to ensure the Prog_enable Signature has been latched.
5. Release the Prog_enable (SDO pin) to avoid drive contention on the Prog_enable/SDO pin.
6. Wait at least 300 us before giving any serial instructions on SDI/SII.
7. Exit Programming mode by power the device down or by bringing RESET pin to 0V.
The question regarding the above basic information is...
If the ATTiny is already powered up, can I jump right to step 3, or does the 20-50 microsecond delay between power up and the application of 12v count?
I am assuming that I can jump right to step 3, which is optimal for my application.
Perhaps someone has tried this and has a real answer?
It will be a few days before I can test this and report back.