In the June 2002 issue we introduced you to the DS89C420, the youngest member of the microcontroller family produced by our ever active friends at Dallas Semiconductor. This controller, although fully downward compatible with other devices from the 8051 series, is much faster and offers loads of extras. This month we continue where we left off by presenting a board which, helped by some free software from Dallas, forms the basis of a powerful yet affordable development system.The 8051 series is still extremely popular with hobbyists as well as professionals. Since the introduction of this microcontroller by Intel in the late 1980’s, a veritable galaxy of development tools, programs and subroutine libraries have appeared which are freely available to anyone with access to the Internet. Although the original controller has been extended with peripheral functions and its clock frequency raised by various manufacturers, the basic architecture of the 8051 core has remained virtually unchanged.