The features of digital fire protection systems are analyzed. To fit the special requirements of digital fire protection systems, the image coding and infrared video coding are mainly provided for a spot fire protection system. According to the Top-down principle, a network model based on the ISO standard is established and its primary top level data flow is given. Both the active and passive communication modes are designed to overcome the limitation by the bad environment. The CPLDTDSP hardware framework and software framework are also discussed.