PURPOSE: To cause no collision of transmission with a transmission converting module even at the time of backup of a host controller, by providing the exclusive dummy command of the transmission converting module on a bus controller.
CONSTITUTION: When a dummy transmitting command is transmitted to transmission converting module 4 from the bus controller 6, a TCM 4 decides whether or not the host controller is in the course of backup and does not transmit a signal unless it is in the course of backup, but detects which sub-loop controller 1 backup is being executed if said host controller is in the course of backup. Subsequently, a transmission destination DA corresponding to the dummy transmitting command is retrieved from a transmission sequence table for a backup which is registered as a table in advance, and following a synchronizing signal SYN, this DA, a discrimination number SA of the faulty sub-loop controller 1 and data D1WDn are added and transmitted.
KIKUCHI SHINYA
SUGANO AKIRA
HITACHI ENG CO LTD