Troubleshooting C-more Screen Changes from a DL05 PLC

The reported DL05/C-more panel changes normally below screen 7 but fails at screen 7 or 9; first check the screen-change value’s interpretation and destination before changing PLC logic. The panel was identified as a full-color C-more, not a Micro, so a Micro-only screen-select workaround is not automatically applicable.

Stop changing data types as a guess

Changing the PLC value or the C-more tag type at random can make one screen number work while creating a mismatch elsewhere. First establish what numeric value the PLC writes, how the C-more tag interprets that value, and which screen the command targets.

• Do not convert to BCD yet. BCD and integer/binary representations agree for decimal values 0 through 9, so a BCD-versus-integer mismatch alone does not explain a failure at screen 7. It can produce different bit patterns at decimal 10 and above.
• Do not treat a hex display in PLC status view as proof that the PLC is using the wrong value. A word shown as hexadecimal may represent a numeric value whose decimal interpretation is what the HMI expects. Compare the raw word and the configured tag interpretation.
• Do not reserve screen 99 as an immediate fix. That workaround was described for a C-more Micro screen-select-memory behavior. The reported installation specifies a full-color C-more, and screen 99 must not be used if it is already assigned.

Record the current screen-change tag address, its PLC value, its C-more data type, and the target screen at the moment of failure. Back up the project before modifying ladder logic or HMI settings.

Separate encoding faults from screen-target faults

The symptom can come from distinct mechanisms. Use the value and navigation behavior to choose the branch instead of assuming every lockup has the same cause.

The reported status view displayed “C” for screen 12 and “F” for screen 15. Those are hexadecimal representations of decimal 12 and 15, respectively. That observation makes the data-type branch worth checking, but it does not establish the configured C-more type or prove that encoding caused the reported screen-7 failure.

Trace the PLC value at the change condition

1. Monitor the screen-change tag online and note its value immediately before, during, and after the condition that requests screen 7 or 9. Record the displayed format and determine the intended decimal screen number.
2. Inspect the PLC logic that writes that tag. Confirm that the condition actually executes and that a later rung or routine does not overwrite the requested value during the same scan.
3. Check the C-more tag database entry for the corresponding PLC address. Compare its configured data type with the value the PLC is supplying; inspect the HMI screen-change configuration for how that tag selects a screen.
4. Repeat with a known working screen value and compare the PLC word, the tag type, and the resulting panel screen. Test one screen at a time so a conditional branch does not obscure the result.

If the PLC value is not the intended number, repair the logic that calculates or writes it before changing the HMI interpretation. If the PLC value is correct but the panel interprets the word differently, align the tag types or deliberately convert the value at a defined interface.

Match the C-more tag to the PLC representation

Use one consistent representation from the PLC screen-change tag through the HMI tag. The reported troubleshooting options were to configure the C-more tag as integer to match a decimal PLC value, or convert the PLC value to BCD and configure the C-more tag as BCD. Pick one method, document it, and verify with screen numbers both below and above 10.

• Direct integer path: Keep the PLC’s numeric screen value as an integer and select the matching integer type for the C-more tag. Confirm in the project that this is the actual type available for the panel/tag configuration.
• BCD path: Convert the source value to BCD in the PLC, write the converted result to a separate tag, and configure the corresponding C-more tag as BCD. Do not point the HMI at the unconverted source tag.

An example discussed for a DL05 uses V2000 as the decimal source and V2001 as the BCD destination:

SP1 --||---- LD V2000
              BCD
              OUT V2001

These addresses are illustrative, not established addresses for the reported machine. Confirm the instruction form and operand requirements in the DL05 programming environment before using it. Verify the destination value in PLC status view and configure the HMI to read the destination tag—not the source.

Inspect every screen-change button and condition

A panel that appears frozen may still be running; the operator may simply have no valid navigation path. A copied screen can retain a button that points to its original destination. On each affected screen, inspect the target configured for every screen-change button, including buttons copied from another screen.

1. Open the screen that fails and inspect each navigation button’s configured target.
2. Compare those targets with the intended screen numbers and with a working screen’s buttons.
3. Check whether a PLC condition continuously rewrites the screen-change tag while the operator uses the panel. If it does, determine whether that repeated command is intentional.
4. Provide a valid home or previous-screen path where the application design calls for one, then test navigation in both directions.

Do not infer a tag-type fault just because one screen is unreachable. A wrong button target is an HMI project configuration fault; changing PLC data representation will not repair it.

Use the Micro reselect workaround only on a confirmed Micro

A separate reported behavior involved the C-more Micro: after PLC logic selected a screen, an operator navigated to another screen, and the PLC tried to select the original screen again, the panel did not change because the screen-select memory still contained the same value. The proposed ladder workaround compared the current Micro screen with the requested screen and, when they matched, wrote a different screen number such as 99 before selecting the requested screen again.

Apply this only after confirming the installed panel is a Micro and reproducing the unchanged-value condition. The source installation identifies a full-color C-more, so first check the exact panel model and its programming documentation. If using an intermediate screen number, confirm it is valid for the project, cannot be selected by normal operation, and is not assigned another purpose; the example explicitly reserved screen 99.

Verify screen changes across the full operating range

After making one controlled change, test both the operator path and PLC-command path. Confirm the panel leaves a working screen, reaches the requested screen, and remains navigable after the triggering condition clears.

• Test a known working screen, screen 7, screen 9, and any screen above 9 used by the application.
• For values above 9, compare the intended decimal number with the PLC word and the C-more interpretation. The observed “C” for 12 and “F” for 15 are useful checks of hexadecimal display versus decimal value.
• Navigate away from a PLC-selected screen and trigger the PLC selection again. This specifically tests whether the panel accepts a repeated request after operator navigation.
• Test the affected screen’s buttons and any return/home navigation, then confirm that the PLC condition does not immediately force an unintended screen.

If a test fails, capture the PLC tag value, data type, current panel screen, requested target, and condition state at that instant. Revert the last change if it creates new navigation faults; do not stack unverified conversions and workaround logic.

FAQ: Diagnose DL05 and C-more screen changes