Could now solve the problem. Since CrisOS is derived from OpenWRT I checked some documentation on openwrt.com how to change the kernel configuration.
Configuring the kernel is done by make kernel_menuconfig (instead of make kernelconfig with devboard-R2_01) Then a menu similar as in the devboard-R2_01 SDK appears and the RTC support can be set as described in http://www.acmesystems.it/?id=57#14100 <http://www.acmesystems.it/?id=57#14100> Now I can access the RTC in the usual way. There seem to be two different programs hwclock within the SDK. I chose the one included in busybox make menuconfig Base system -> busybox configuration -> Linux System Utilities -> (x) hwclock Klaus
