PURPOSE: To enable to inspect the operating condition of the data processor even ON-line, by shunting the memory content of a plurality of control registers to a plurality of back up registers, with the shunt control unit.

CONSTITUTION: The control registers 5-1...5-9 are controlled with microprogram, and the memory content of the selection control register selected from the registers 5-1...5-9 is respectively stored in the back up registers 7-1...7-4. Further, when the micro instruction predetermined is executed, the shunt of the memory content of the registers 5-1...5-9 to the registers 7-1...7-4 is controlled with the shunt control unit 6. In this case, the memory content of the registers 5-1...5-9 stored is individually or simultaneously displayed, allowing to inspect the operating condition of the data processor even ON-line.