PURPOSE: To attain the check of memory content of all processors by using a bus connector and a DMA controller enabling to set an address and data word number externally by a specific data on a bus so as to use a check control program only.

CONSTITUTION: In detecting a data with a specific identifier on a data bus 10 by a bus connector 21, it is written in a register 25 and a DMA controller 22 applies direct memory access with a memory 23 accordingly. When a check exclusive processor 50 reads a data of a specific processor unit 20 connected to the bus 10, since the unit 20 returns a designated data onto the bus independently of the software by sending the data representing a processor identifier, a DMA address and a word count and a data representing the direction of data to the bus 10, the data is realized and checked by displaying onto a terminal 30 connected to the processor 50.