R4F with multiple or nested Interrupts

I am using E2S 5.4.0.018, KPIT GNUARM-NONE-EABI v16.01 Toolchain, RZ/T1

I need nested or multiple Interrupts on the R4F. It seems not so easy as described in the RZ/T1 Users Manual Hardware. When i set only CPSR.I to 0 in the interrupt service routine the program crashes.

What is wrong?

The interrupt service routine is declared with __attribute__((interrupt ("IRQ")));

This works fine if the interrupt is not nested, but didn’t work in my case.

Any further Hints, sample Code.