Arduino Attiny85 RS485 half duplex - not programming

[expertup]

I downloaded all repo, and install all libraries on windows. Compilation work correctly.

But I have problem programming Attiny85 on arduino via bootloader with RS485. On direct programming (rx/tx without RS485), arduino detects attiny and programs it. After soldered SN75176AD, connects to A/B converter USB - RS485, nothing happens. I see change state pin in attiny (PB2) for switch SN75176AD mode, but arduino not start programming.

What I'm doing wrong?

Command used for compilation:
make attiny85 BAUD_RATE=19200 RS485=B2 TIMEOUT=8

I saw #305 and #320 but I wonder who starts the 1st transmission when programming, I am thinking about the "hand shake". I can't find specific information, step by step. I would have to connect the oscilloscope and "see" the transmission, to understand what is really going on.