PURPOSE: To enable testing of status of hardware and software in an on-line state by providing respective communication route selectors between each communication control unit communication route of a duplex redundancy processing system and thus constituting a folding communication route.
CONSTITUTION: CPU10 and CCU20 of an in-use system are connected to an upper- rank station 2 by a selector 30 through a communication route L1, and CPU10 and CCU20 of a spare system are not connected to the upper-rank station 2 by a selector 30' and they are in a stand-by state. When testing, selectors 30, 30' are controlled by a processor for testing 50 and a route of CCU20, a selector 30, a channel L2 and CCU20' is formed. The data sent from CPU10 are transmitted to CPU10' through the CCU20, selector 30, channel L and CCU20'. By this, the state of receiving by CPU10' of the data sent out from CPU10 can be detected with a comparator 40. Consequently, the status of hardware and software can be tested in an on-line state.
MASUO KAZUYUKI
KAWASAKI ICHIO
AOKI TOSHIROU
MORI MAKOTO
NIPPON TELEGRAPH & TELEPHONE
OKI ELECTRIC IND CO LTD
NIPPON ELECTRIC CO
HITACHI LTD