| 摘要 |
PURPOSE:To decrease the number of control lines for securing a transmitting circuit, by coupling a main controller and plural subsidiary controllers to a common bus by control lines of 3 kinds such as clock, transmission request and transmission permission, and executing a time division multiplex control. CONSTITUTION:A main controller 201 and N sets of subsidiary controller groups 202-204 are connected by control lines of 3 kinds such as a clock signal line 205, a transmission request line 206 and a transmission permission line 207, as well as a data signal line 208. In order to detect whether a transmission request from a subsidiary device exists or not, the device 201 sends out N pieces of pulse trains to the subsidiary device group through the signal line 205. Each subsidiary device receives and counts the pulse train, and sends back an answer to the device 201 as to whether the transmission request exists or not, through the request line 206, by a clock timing which has coincided with its own device number. The device 201 checks an ordinal number of a pulse train of the transmission request which is sent back, stores a number of the request device, and sends out a transmission permission pulse to the permission line 207 by a timing of a device number to be answered, of each pulse on the signal line 205, in accordance with a prescribed priority rank, by which the transmitting circuit is secured. |
