Knowledge Base / Rockwell In-chassis / CompactLogix / MVI69 Series

My MVI69 module is not working. What might be wrong?

Search KB


There are many things that may prevent a MVI69 module from working properly.  Here is a list of the most commonly overlooked items that can prevent it from working as expected:

1.  The Prosoft provided sample ladder logic OR Add-On Instruction (not both) must be loaded into your CompactLogix controller, or included into your existing application.  This includes I/O configuration, user-defined datatypes, controller tags, and ladder logic.

2.  The CompactLogix CPU must be in RUN mode.  The module has to see the processor operating on the 1769 I/O bus before it can complete its boot routine and begin normal operation.

3.  The MVI69 modules need 800mA of 5vdc current from the backplane.  If the power supply is inadequate, the module will not function normally.

4.  The MVI69 modules have a Power Supply Distance Rating of 2.  This means they can be installed immediately next to the 1769 power supply on either side or be installed so that there is no more than one other module between them and the power supply one either side.  For 1768-L43/45 systems the power supply distance rating starts at the processor and the beginning of the 1769 bus.  So the module must be next to the 1768-L43/45 processor, or at most one slot away.

5.  Be sure you have a right end cap (1769-ECR) installed to the right of the rightmost I/O module in the system.  Without this end cap, the 1769 bus is not properly terminated and the MVI69 modules will not operate correctly.

6.  Be sure that in the I/O Configuration section of the ladder logic, on the Connection tab for both the CompactBus Local and the MVI69 module, that the "Inhibit Module" box is NOT checked.