HOST INTERFACE CONTROL SYSTEM FOR PRINTER

PURPOSE:To simultaneously access from a plurality of host apparatuses and to enhance the efficiency of the apparatuses by adding priority order to n pieces of input ports and so controlling as to release a service for a presently selected port when no access occurs for a predetermined period. CONSTITUTION:When an interrupt request is generated from a first timer 5, a CPU 4 transfers an entry jump to idle by this interrupt routine when no input port is served, and sequentially transfers from FiFo having smaller input port number. Accordingly, the smaller input port number has higher priority, and the CPU 4 inspects a data presence signal (f). Here, when any signal (f) is OFF, the interrupt is ended as no data exists. If an interrupt request is generated from a second timer 6, the entry used during interrupting of the timer 5 is directed idle to end the process. Thus, a service for other input port can be performed.