Topic: DMD0201
Using a Link to Connect to a Do-more Controller
Connecting to a PLC with an Offline Project Already Open
After opening an offline Do-more Designer project, connecting to a Do-more controller is done by selecting PLC-> Connect from the menu and highlight one of the preconfigured communication links, then click Select to go online with the controller that link is configured to use.
Select - attempts to go online with the controller that link is configured to use then compares the contents read from the controller with the contents of the offline project to make sure they completely match.
Cancel - returns to the offline state
Add... - opens the Link Wizard to begin the process of creating a new communication link.
Edit... - opens the Configure Link dialog which can edit the settings of the highlighted link.
Delete - deletes the highlighted link.
Help - invoke the Help for managing communication links.
Link Enabled - this box will be checked if the highlighted link is functional. The functional state of each preconfigured link is checked when Do-more Designer is started.
Connecting to a PLC with No Project Open
Clicking the New Online button of the Online toolbar and selecting one of the preconfigured communication links, or double-clicking one of the preconfigured links in the Launchpad will attempt to go online with the controller that link is configured to use.
If Do-more Designer successfully connects to the controller it will check to see if there's a project loaded into the controller. If so, Do-more Designer will then check the current projects folder to see if there is an offline project by that same name. If a project by that same name is present on disk, this message box will be displayed asking to open the disk-based project that matches the project in the controller.
Yes - go online with the controller, open the offline project, and compares the contents read from the controller with the contents of the offline project to make sure they match.
No - go online with the controller and create a new project named Untitled, then read all of the controller's contents into this new project.
Compare Online and Offline Projects
In the two cases above where there is both a disk-based project AND a controller-based project being accessed, Do-more Designer will compare the contents of the two projects when the connection to the controller is established. If the projects differ in any respect the following dialog will be displayed, telling the programmer that differences exist.
The Details section will list which of the four main components of the project - System Configuration, Program (code-blocks), Documentation, and Memory Image - are different.
If the Program section contains differences, click the Compare Programs... button to open that utility which will generate a detailed listing of those differences.
If the Memory Image Configuration or the Memory Image Data is shown to be different you can click the Compare Memory Image Configuration and Data... button to display a listing of the differences:
The following lists the possible messages you can see in this dialog and information on how to resolve the issue:
Error Reading Region or Data - a communication error occurred while trying the read the Memory Image data from the PLC.
Incompatible Memory Configurations - the memory configuration for the region in the PLC is different from the memory configuration of a region by the same name in the Memory Image file. No comparison can be done. Use a Write to PLC or Write to Disk operation to synchronize the Memory Configurations between the PLC and the offline project. Then you can use the Memory Image Manager to compare the Memory Image file contents.
Exists Only Offline - the region is not part of the Memory Image file in the PLC. Use a Write to PLC operation to download the Memory Image file to the PLC.
Exists Only Online - the region is not part of the Memory Image file stored on Disk. Use a Write to Disk operation to save the Memory Image file to disk.
Ranges Do Not Match - the region exists in both the PLC copy and the offline copy of the Memory Image file but the range of data in the regions are different. Determine which copy of the Memory Image file has the correct range and use a Write to PLC or Write to Disk operation to get the correct range into both copies of the file.
Ranges Match, but Online Data was Unavailable - the region exists in both the PLC and the Memory Image file, the range of the region matches in both places as well, but the data within the range could not be read from the PLC to do a comparison. This will result if the On Connect option in the Memory Image Manager was set to "Don't Compare On Connect" because the Memory Image data will not be read from the PLC.
Data Does Not Match - the region exists in both the PLC and the Memory Image file, the range of the region matches in both places as well, only the data within that range that is stored in the offline copy does not match the data currently in the PLC. Determine whether the correct data resides in the PLC or in the Memory Image file then use the Memory Image Manager to refresh the contents of the data in the Memory Image file, or download the copy of the data from the Memory Image file to the PLC.
To continue online you must select which copy of the project to display in Do-more Designer:
Go Online and View the DISK Project - selecting this option will display the offline copy of the project.
Depending on the types of differences between the offline and online versions of the project, making this selection can cause a variety of changes that will be made to the version displayed in Do-more Designer that will have to be resolved before the project can be downloaded to the PLC.
One of the more important changes that is possible happens if the CPU type in the Do-more Designer project does not match the CPU type of the online PLC. In this instance the CPU type in the Do-more Designer copy will be changed to match the online PLC's type, and any references in the displayed project to hardware resources of the CPU that no longer exist will be removed and noted in the Output Window. Refer to the Setup Offline PLC help topic for more details on the types of issues that can arise from changing the CPU type of a project.
After making this selection, note that the Write to PLC button on the Online Toolbar is enabled as shown below:
This indicates that there are differences between the project in Do-more Designer and the PLC. Click the Write to PLC button which will open the Project Download dialog to synchronize the projects by downloading the offline copy of the project to the PLC.
Go Online and View the PLC Project - selecting this option will display the copy of the project that was read from the PLC.
Note that the Save button on the Offline Toolbar is enabled as shown below:
This indicates that there are differences between the copy of the project in Do-more Designer and the copy stored on Disk. Click the Save button to synchronize the projects by copying the Do-more Designer copy of the project to Disk.
Cancel, and Return to Offline - selecting this option will abort the attempt to open a connection to the PLC. Do-more Designer will return to the offline version of the project.
Note: there is a special case in resolving the online/offline differences that involves Edge BitsEdge Bits hold the scan-to-scan state of the edge-triggered inputs. The value of an Edge Bit is assinged when the project is downloaded to the CPU. Edge Bits are automatically added to the project by Do-more Designer and are for internal use only. and Instruction IDsA unique number that is added to each instance of certain ladder logic instructions to help manage device usage. The value for an Instruction ID is assigned when the proiject is downloaded to the CPU. Instruction IDs are automatically added to the project by Do-more Designer and are for internal use only.. These elements are assigned values only when the project is downloaded to the PLC. Which means that if a new instruction that has an edge bit is added to the project and downloaded to the PLC, it's value in the copy in Do-more Designer will match the PLC value, but it will NOT match the value in the project that is on DISK.
When this happens after clicking the Write to PLC button, notice the Save button on the toolbar will be enabled, meaning that you need to Save the project to Disk again so that the new Edge Bit / Instruction IDs in the Disk copy of the project will match the values that are in the PLC. The following message will also appear in the Output Window after the Write to PLC operation:
[Message] Program modified - new Edge/Instruction IDs assigned at download.
Multiple User Session Warning
Do-more controllers can support multiple concurrent online sessions with Do-more Designer. In situations where more than one online session is changing the project stored in the controller, whenever one session writes changes to the controller, the other online sessions will receive the Attention! notification displayed to the right.
This could be changes to the System Configuration, the ladder logic, or the documentation. The proper course of action is to disconnect and reconnect at the first opportunity. This will prompt Do-more Designer to run a Program Compare so the differences can be resolved.
See Also:
Connecting to a Do-more Controller
Using the Link Wizard to Create New Communication Links
Using Configure Link to Modify Existing Communication Links
Using Link Info to Monitor Communication Links
Related Topics: