PURPOSE: To provide data transfer by a data transfer controller interposed between a main storage device and a peripheral device and a fault detection system for the data transfer.

CONSTITUTION: A comparator 10 compares the value of a specific bit of a request information storage buffer 4 which stores and holds a request command to the main storage device with the value of a specific bit of a reply information storage buffer 7 which stores and holds reply information from the main storage device, a comparator 13 compares the write addresses of a register 8 and a register 9 with each other, and a comparator 14 compares the read address of a read address register 12 with the indicated read address carry-about number of the reply information storage buffer. The results of the respective comparators 10, 13, and 14 are received by a data transmission control circuit 11 and the read address register controls and holds the read address of the reply data storage buffer 6 according to the indication from the data transmission control circuit 11, thereby transferring data between the main storage device and peripheral device and detecting a fault in the data transfer.