I know what putty is; I just never saw any options specific to a windows program appear in a BIOS...
the port is a standard rs232 over rj45 i assume - as said I get the full console output, only keystrokes are not registered by the unit.
Usually this is because of mismatching flow control, but default is disabled and that's whats set at the BIOS and emulator. I also tried explicitly setting -fn although screen doesn't enable it by default and It works OOTB with just "screen /dev/ttyU0 115200" with any other gear - only the topton unit will not register any input...
Also tried with FC enabled on both ends, but as said: no combination of parameters will give me keyboard input.
I'm currently suspecting either a non-standard wiring (RX pin) or a defective port.
EDIT:
Mystery solved - the pinout is different to cisco and most other gear using RJ45 serial ports. Coincidently, pin 6 is also TX on the topton, that's why I got console output, but the RX pin is at pin 5, not 3 (cisco et al).
Found an old Allied Telesyn cable while searching through my cable collection for something with a soldered DB9-connector where I could crimp on an RJ45 connector, but that cable worked 'as is' so I'm using that for now...
TL;DR
The RJ45 serial pinout for those units is NOT identical to (most) network gear!
At least the important pins (RX/TX, GND) seem to correspond with Allied Telesyn:
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