Hi everybody! I'm using a uC ADuC842 (based in 8052 core). It has 2 KB of XRAM On-Chip. I have a test program (C code) which do some operations with float numbers and send results to the serial port. When I use this compiler configuration: - Memory Model: small: variables in DATA - Code ROM Size: Large: 64K program I haven't any problem and compiled code runs perfectly in ADuC842. When I change compiler configuration to: - Memory Model: Large: variables in XDATA - Code ROM Size: Large: 64K program - Check Boxes selected: + Use On-Chip ROM (0x0-0xF7FF) + Use On-Chip XRAM (0x-0x7FF) I simulate compiled code with uVision and it runs perfecly (like before), but when I run compiled code in ADuC842 it doesn't work. It seems that I have problems using XRAM, but I don't know where. Sombody can help me? Comment: I have researched along the Disscusion Forum and I have read that it's necessary use startup.a51 to initialize uC. I don't know how call that segment in my C code program. Can this solve my problem? Thaks!!