simulation runs now but processor aborts at instruction 12

Time: 1800230 ns  Iteration: 2  Instance:
/tb_top/i_top/i_lcd_core/i_lcd_fifo
** Fatal: (vsim-3421) Value 17 is out of range 0 to 13.
Time: 1800230 ns  Iteration: 2  Process:
/tb_top/i_top/i_tempomat_cpu/cpu_cycle File:
../vhd/tempomat_cpu_rtl.vhd
Fatal error in Process cpu_cycle at ../vhd/tempomat_cpu_rtl.vhd
line 108)