PURPOSE: To secure the normal actuation of a daisy chain circuit with no cut-off of the daisy chain despite the removed of undesired devices set on a mother board, by providing an internal logical circuit consisting of plural AND means in order to increase the number of wirings.

CONSTITUTION: The 2nd device 20 is taken out of a mother board, and an interruption request signal IREQ is delivered from the 3rd device 30. In such a case, a terminal j3 of the device 30 is set at a high level by a pull-up resistance. If a CPU1 permits an interruption of the device 30, a signal IACK0 is supplied to a terminal j1. Thus the terminal j1 is set at a high level. While the 1st device 10 delivers no interruption request and therefore delivers a signal of a high level via a terminal (k) by the pull-up resistance. Therefore a terminal j2 of the device 30 is also set at a high level, and it is confirmed that the CPU1 has permitted an interruption. Thus a normal function is maintained for a daisy chain circuit without changing the layout of devices and the forms of wirings and even after the device 20 is taken out of the mother board.