hi,

BTW, somebody said that if I attach a switch between VCC and RST plus inverter to PSEN and EA, I won't be able to sink the strong PSEN pull-up. But if I do opposite, attach a switch between ground and PSEN+EA and inverter to Reset...?

Which chip you talk about? To call bootloader with hardware conditions for Atmel chips you must tie EA to V_cc. To keep it all clean, I have made a little picture which shows steps between power up/reset and time when bootloader runs:

You may see here:

- You must not tie PSEN to GND immediately after reset applies. Well, Atmel does not specify time T_AB, but they indicate it anyway;
- You have put PSEN to low level (ground) before falling edge of reset, here: at any time between points B and C;
- Hardware conditions (PSEN=0, EA=1) are sampled at falling edge of Reset (at point C);
- As PSEN is an output pin in normal operating mode, so you should release PSEN after reset comes to low level state (point D). Unfortunatelly, Atmel does not specify time T_CD once again.

Regards,
Oleg