CHANNEL DEVICE

PURPOSE:To improve data transfer efficiency between a MS access control circuit and an I/O interface control circuit by providing an answer transmission means and a request reception means to said access control circuit and an answer reception means and a request transmission means to said interface control circuit respectively. CONSTITUTION:An I/O interface control circuit 200 sends an answer clear instruction and a request signal to a main storage (MS) access control circuit 100 and clears its own stored answer signal. The circuit 100 stores the received request signal and turns off the answer signal based on an answer clear instruction. Then the circuit 100 sends a request clear instruction and the answer signal to the circuit 200 synchronously with the next system clock and clears its own stored request signal. Then the circuit 200 stores the received answer signal and turns off the request signal by a request clear instruction. Thus the data can be transferred between both circuits 200 and 100 at a high speed.