There are provided a CPU connection circuit and a method wherein the CPU connection circuit is a circuit to be employed by two CPUs by alternately conducting a changeover between two buffers disposed therebetween to prevent an event that data processing cannot be fully executed by the CPU on the receiving side. There is included a memory controller 303 which monitors whether or not an amount of data stored by a CCPU 1 in either one of buffers 301 and 302 reaches a predetermined threshold value; when the amount of data stored by the CCPU 1 in the buffer 301, 302 reaches the threshold value, the memory controller 303 requests an ACPU 2 to acquire the data stored in the buffer and changes the storage destination of data from the CCPU to the other one of the buffers; the threshold value is a value more than a unit quantity of data which the CCPU 1 sends to the buffer 301, 302.