EXTCLK on TC299

Hello,

I am using Triboard TC299 running with 300MHz cpu speed and Hightec Free Tool Chain with iLLD. I want to enable EXTCLK0 and EXTCLK1.
In main of core0 after startup I added the following code:

uint16 passwd = IfxScuWdt_getSafetyWatchdogPassword();

IfxPort_setPinModeOutput(&MODULE_P23, 1, IfxPort_OutputMode_pushPull, IfxPort_OutputIdx_alt6);
IfxPort_setPinModeOutput(&MODULE_P32, 4, IfxPort_OutputMode_pushPull, IfxPort_OutputIdx_alt6);

IfxScuWdt_clearSafetyEndinit(passwd);

SCU_FDR.B.STEP = 1023; //fout = fspb/2 * 1/(1024-1023)
SCU_FDR.B.DM = 1; //normal divider
SCU_FDR.B.DISCLK = 0;

SCU_EXTCON.B.SEL0 = 9; // fspb = 100MHz EXTCLK0 should be 50MHz
SCU_EXTCON.B.NSEL = 1;
SCU_EXTCON.B.SEL1 = 9; //fspb = 100MHz
SCU_EXTCON.B.DIV1 = 3; //fspb/(3+1) EXTCLK1 should be 25MHz
SCU_EXTCON.B.EN0 = 1;
SCU_EXTCON.B.EN1 = 1;

IfxScuWdt_setSafetyEndinit(passwd);

Nothing happens on the two output pins ...

Does anybody has an idea there the mistake is?

Thanks in advance
Steffen