This a FREE tool chain which compiles C codes into 8051 binary code, converts the binary to RTL ROM, and simulate in Modelsim. SDCC is the compiler. Example compilation: cd compile sdcc --iram-size 0x80 --xram-size 0x800 t8051.c REM sdcc --iram-size 0x80 t8051.c packihx t8051.ihx > t8051.hex ..\test\mkrom.exe ..\compile\t8051.hex