It is an object of this invention to expand an SBP-3 protocol such that two data buffers can be independently controlled. To achieve this object, a target sends responses to status blocks corresponding to two commands included in one ORB in the SBP-3, and an initiator receives these responses to the commands independently of each other. The number of times of execution and time interval are designated for each command. The target repeats a command the designated number of times at the designated time interval.