Stian,
I have the TS-590S Twin Setup (not TS-590SG).
On the control side I have connected the RRC-1258 COM 2 port (plug male) to the TS-590S COM port (plug female) with pins 2 and 3 crossed (2-3, 3-2) and pins 5,7 and 8 wired straight.
On the radio side I have connected the RRC-1258 COM2 port (plug female) to the TS-590 COM port (plug female) with a straight cable (2-2, 3-3, 5-5, 7-7, 8-8).
The Baud rate (Menu 61) is 9600 Baud and the connection between the radios works fine. The COM1 port on the radio RRC (plug male) is connected to a RA0SMS Kenwood Band decoder (plug male) to send the band information to my Yaesu-compatible Linear amplifier with a crossed wiring. (2-3, 3-2, 5-5, 7-8, 8-7) .
At both sides the Radio and Serial settings are the same:
Radio settings: Program mode 18 - Kenwood 590 Twin.
Serial settings:
COM2 mode: Logical parallel with COM0.
COM1 mode (for the band data transfer): Mode-7 CAT to COM2 (remote / local to remote)
I could not get the N1MM+ logging program to work with COM1 on the control side, so I used a direct USB connection between the TS-590S and the PC
with 115200 baud (menu 62). This works fine.
I helped testing both Transceivers side by side before deploying one to the remote site.
The only problem I have with the TS-590S Twin setup is that the M/V and the Split functions do not work. My firmware version is V.2.05.
Maybe a downgrade to V.2.00 could help in this matter. I can live without the memory channels but the Split function comes in handy when working DX stations.
I now use a workaround with the RIT button.
73 de Christian, HB9BJL