PURPOSE: To obtain the pseudo state of input transfer operation of a channel device by providing the channel device with a pulse generating circuit, a selector, etc. and generating a pseudo strobe signal at the time of diagnosis inhibited the use of a peripheral control device.

CONSTITUTION: At the normal time, a data transfer control part 8 controls the operation of a data input register 3 or the like by a strobe signal supplied from the peripheral control device 106 through a signal line 53. At the time of diagnosis, the control operation is performed by a pseudo strobe signal outputted from a pulse generating circuit 22. Normally, a selector 21 inputs transfer data transferred from the periphery control device 106 and outputted from a receiver 14 to a data input register 3, but when an FF20 is set up, inputs the output of the register 2 to the register 3. Thus, the pseudo state of the input and transfer operation of the channel device can be obtained by connecting the pulse generating circuit, etc. and generating the pseudo strobe signal.