Method for system bus supporting in voice mail board

PURPOSE: A system bus support method of a voice mail service board is provided to set automatically the voice mail service board as a PB bus mode or an X bus mode according to a bus structure of a PBX(Private Branch Exchange) recognized by a back board connected directly to the PBX, thereby capable of operating the voice mail service board irrespective of the mounted PBX bus structure. CONSTITUTION: A CPU(Central Processing Unit) reads out the value of a bus selection register(S30). Thereafter, it is discriminated whether the value is set by 0, that is, a voice mail service board will use a PB bus(S32). If the value is set by 0, an interrupt is set by '1' in order to receive the interrupt signal applied from the PB bus, tasks by functions required to the voice mail service board are produced respectively(S34,S36). After producing the tasks, a PB bus interface task is produced in order to process the interrupt signal generated from the PB bus(S38). Thereafter, the task reads out the message from the PB bus and transmits the transmission message to the PB bus according to the interrupt signals generated from the PB bus periodically, thereby performing the voice mail service function(S40).