Patent ID: 6671840
Filing Date: 2003-12-30
Classification: G01R,Y02P

Abstract:
A communication system comprising:a plurality of boundary scan elements, each boundary scan element including a plurality of boundary cells individually assigned to respective input terminals and output terminals, a TAP circuit for controlling input and output of data to or from said boundary cells, a TDI terminal for inputting serial data to be supplied to said boundary cells, a TDO terminal for outputting data from said boundary cells as serial data, a TCK terminal to which a clock signal is input, and a TMS terminal to which a mode signal for switching the operation mode of said TAP circuit is input; a plurality of terminal units connected to said respective boundary scan elements or provided with ICs into which the elements are incorporated; a communication controller, connected in series with said boundary scan elements, for transmitting/receiving through said boundary scan elements communication data for individually controlling said terminal units; and a cable provided to establish connections between said boundary scan elements adjoining each other and between said boundary scan elements and said communication controller, said cable being formed by binding up a clock signal line, a mode signal line, an outgoing communication line, and incoming communication lines, wherein said incoming communication lines establish individual connections such that the TDO terminal of one of the boundary scan elements positioned at a backmost as seen from said communication controller is connected with the TDI terminal of another of the boundary scan elements positioned at a side nearer to said communication controller than said one at the backmost, and a data input terminal of said communication controller and the TDO terminal of another of the boundary scan elements positioned nearest said communication controller are directly connected with said communication controller at an end portion of said incoming communication lines through a cable, and said outgoing communication line establishes a connection between a data output terminal of said communication controller and said TDI terminal of said boundary scan element positioned at the backmost as seen from said communication controller.