| 摘要 |
A communications network is used to couple weld controllers and different operator interface units together, regardless of their data structures. An arbitration system provides a means for one operator interface unit to communicate to a selected weld controller at a given period of time. The operator interface units have one of three modes of operation. These include database master, primary master, and secondary master. During setup of the communications network, the master devices are assigned a physical address that defines the its type and priority within the network. The database master is the only device which can automatically download data to a weld controller. It has the highest priority as a network arbiter. The primary master will act as the network abitrator in the absence of a database master. A secondary master must listen for an access grant from the current network arbiter, before initiating a message packet on the network. When no database or primary device exists on a network, the secondary device with the highest priority, as defined by its address during startup, assumes the role of network arbitrator. |
