s51, sz80 shc08 and sstm8 are free open source simulators developed by Daniel Drotos. The simulators are built as part of the build process. For more information visit Daniel's web site at: http://mazsola.iit.uni-miskolc.hu/~drdani/embedded/s51. It currently supports the core mcs51, the Dallas DS80C390, the Phillips XA51 family, the Z80, 6808 and the STM8.