![](/images/new-backgrounds/1314959/314959111x1.webp)
COMMUNICATION | EXCEL 50/100/500/600/800 |
trollers and devices to exchange data such as measured values, alarms log, and trends. This means that values from one controller or device can be sent to the entire system.
Besides allowing communication between controllers and devices, the
When a controller does not have a modem directly connected, the
Access
The
The flow of data between devices can be structured hierarchically as part of the software in the user program. Structuring data exchange means defining what infor- mation can be exchanged between which bus devices. Communication is still carried out on the
Bus Initialization
When your system first starts up, the software runs a check to see what devices are connected to the
During initialization, the bus master requests information about global datapoints from each controller. At the same time, the controllers store the address of the device making the request so that the controllers can subsequently transmit the appropriate data to the appropriate device.
After initialization, each controller knows the address of the next controller with the right to transmit data. If a controller now stops communication, the bus master recognizes that this controller is no longer online and interrupts token passing. As a result, the
Bus Communication
The Excel 50/100/500/600/800 controller does not transmit any
See "Global Datapoints" on page 11 for details on defining global datapoints. During normal operation, the bus master transmits active values. The bus master transmits only values which have changed or which have been requested by another device on initialization or when a device has been offline.
This method of exchanging data reduces the load on the bus and means controllers store only the data they need for their own communication.
I/O Runtime Synchronization
XF525 After application download and after a power failure a runtime synchronization takes place which takes the complete runtime as defined in the datapoint description plus an additional 10%.
54 |