Control Studio's On-line mode is a powerful tool for confirming a module's correct operation and for diagnosing module problems. You must assign and download a module before you can view it in On-line mode.
Open the module in Control Studio.
On the Home tab, in the Diagram Mode group, click On-line to create an online session in which you can examine module and block parameters.
If the module is operating correctly, the outputs are displayed next to the block.
If there is a problem with a function block, a red X appears on the function block. To determine the source of the problem, perform the following steps:
Check the BLOCK_ERR parameter (double-click a parameter to edit it) and determine if the block is out of service (OOS) or if it has a block configuration error. Among the problems that can cause a block to be out of service are misconfiguration, bad sensor input, and problems with the download.
Check the status of the block's input and output parameters. For example, a status of BadNoCom indicates that information is not being sent to the block's inputs.
If the block has a bad PV, verify that the correct XD_SCALE, UNITS, and RANGE are transferred.
If the data has intermittent bad status, check the required macrocycle and the module execution rate. The module execution rate should be >= 2 times the actual macrocycle.
Remember that if you make any changes in On-line mode, the changes are not saved in the database. Use Control Studio or Explorer to upload the changes to the database.