Avoid reboot when connecting USB cable

[ves011]

I have my own ESP32S3 board which is very simple. It has ESP32-S3-WROOM-1 module with reset circuit and switch, boot switch and a 16p connector to access some pads. Communication with board is via USB Serial/JTAG controller pins 13 and 14 (IO19, IO20)
Strapping pins are left unconnected.
The power is provided by an external supply and my USB cable has only 3 wires D+, D- and GND
Whenever i plug the cable ESP goes through a reboot cycle. Can this reboot be avoided?

[ESP_LJH]

Please enter into UART0 download mode, then reboot could be stopped. Or if flash is not empty, there should be no reboot.

[ESP_Sprite]

In general, USB shouldn't do a reboot cycle by itself. What software are you using to look at the serial monitor? Perhaps it wiggles DTR/RTD in such a way that it resets the ESP, 'idf monitor' does that by default iirc.

[ves011]

I agree USB shouldnt do a reboot by simply connecting the cable.
In this case i'm thinking maybe because USB PHY is shared with JTAG logic, some signals have multiple meanings....
I tried with GPIO3 shortcutted to ground to force JTAG signal from on-chip JTAG pins, but same result.

The software i use is teraterm. Looking into settings dowsen't tell anyting about control signals. I tried putty, but same problem.