I have a small program (991 byte). I use the C51 options LEVEL 8. The ISD51 will work correkt. If I change to LEVEL 6 the size of this program is (1020 byte). After the program with FM and a change to the simulator I'll get the following message: ------------------------------------------ "ISD51 Error" Loaded application does not match ROM content! Please program your application into the ROM of your target system again. ------------------------------------------- I have checked the FLASH. The program code is correct. Can anybody help me ? Thanks