| 摘要 |
PURPOSE:To improve reliability of communication data by comparing and collating the data that represents counted value of a peripheral counter in the command of transmitting side with counted value of a peripheral counter of receiving side. CONSTITUTION:When data processing unit CM1 is made specified data processing unit, a peripheral counter for a specified station is provided in it, and a peripheral counter for a general station is provided in other data processing unit. Specified data processing unit CM1 adds numerical value ''1'' to peripheral counter for the specified station of its own station everytime when command is transmitted, and sends out putting it in the command. Everytime when command is received, other data processing units CM2-CM5 add numerical value ''1'' to the peripheral counter for the general station of its own station, and compare this counted value and counted value of the peripheral counter for the specified station in the command. In such a way, the omission of receiving of command can be checked, and the spreading of abnormality due to communication error to the whole plant which becomes controlled systems PR1-PR3 can be prevented. |
