Data transfer unit for small computer system with simultaneous transfer to two memories and error detection and rewrite to substitute address

摘要

A data transfer unit for a small computer system which has a host computer and main and auxiliary storage units, transfers data between the host computer, and the main and auxiliary storage units. The data transfer unit transfers the data, which is outputted from the host computer, from the data buffer to both the main and auxiliary storage units simultaneously, in an operation mode in which data is transferred from the host computer to the storage units. When an error occurs in the main or the auxiliary storage unit, the data transfer unit transfers the correct data from the other storage unit which is operating normally, to a substitute address in the storage unit in which the error has occured.