PURPOSE: To continue control and arithmetic as the information processor even in the case of any abnormality at a transmitting function by interrupting a main transmission processing program, calling a program counter value and a stack pointer value and continuously processing an interrupted information processing program when processing time exceeds the set time of a monitoring timer.

CONSTITUTION: A main transmission processing program S4 equipped with a priority level higher than that of an information program S2 is arranged, and the monitoring timer constituted as one part of this main transmission processing program S4 and equipped with the set time within the term of routine interruption is provided to monitor the transmission processing time. That monitoring timer monitors the transmission processing time and when this time exceeds the set time of the monitoring timer, transmission abnormality is decided. Then, the main transmission processing program S4 is interrupted, the program count value and the stack pointer value stored in a memory 3A are called, and the interrupted information processing program S2 is continuously processed. Therefore, even when any abnormality is generated at the transmitting function, the control and arithmetic of an information processor 1 can be continued.