RS485 on SH4 using devc-sersci

I cannot toggle the RTS pins on a SH4.
The serial driver I am using is loaded via:
devc-sersci -b2400 -u 2 -h -f -c33333333/16 sh7760scif2

I have been trying the QNX example … evctl.html
but no success to toggle the RTS line.
Sending/receiving chars works fine.

Anyone ever used RTS with the devc-sersci driver?