The 87C576 includes two separate methods of programming the EPROM array, the traditional modified Quick-Pulse method, and a new On-Board Programming technique (OBP). Quick Pulse programming is a method using a number of device pins in parallel (see Figure 1) and is the traditional way in which 87C51 family members have been programmed. The Quick-Pulse method supports the following programming functions: – program USER EPROM – verify USER EPROM – program KEY EPROM – program security bits – verify security bits – read signature bytes The Quick-Pulse method is quite easily suited to standard programming equipment as evidenced by the numerous vendors of 87C51 compatible programmers on the market today. One disadvantage is that this method is not well suited to programming in the embedded application because of the large number of signal lines that must be isolated from the application. In addition, parallel signals from a programmer would need to be cabled to the application’s circuit board, or the application circuit board would need to have logic built-in to perform the programming functions. These requirements have generally made in-circuit programming using the modified Quick Pulse method impractical in almost all 87C51 family applications.