A DL05 PLC can use the C-more Micro’s physical function-key data to select screens, with the screen-selection logic kept in the PLC. The working approach is to read the HMI button word, turn each key press into a one-shot event, and use that event to select the intended screen or advance through its assigned screens.
Check that the HMI is sending button data
Read the PLC-side value configured to receive panel button presses. In this installation, the C-more Micro stored the pressed-button value in V2071. Press one physical function key at a time and watch whether the value changes. Treat that address as an installation-specific configuration, not a universal C-more Micro address.
- Open the C-more project and inspect the Panel->PLC data transfer settings. Confirm that the pressed-button value is assigned to the PLC location you are monitoring.
- Monitor that PLC location while pressing and releasing each key. Record the value for each individual press and its released state.
- If the value does not change, check the HMI transfer assignment and PLC address before writing screen-selection logic. If the value changes, continue by decoding the bits.
Keep the direction of the data transfer clear: the panel sends the button status to the PLC, while the PLC sends its selected screen or other display data back to the panel. A correct PLC rung cannot react to a key press if the panel is writing to a different address than the rung reads.
Decode the button word before assigning screens
The reported V2071 value is a bitmask, so more than one bit may be represented in the word. The described mapping is:
| Bit position | Reported button | Engineering check |
|---|---|---|
| 0 | Button 1 | Press only the corresponding key and confirm bit 0 changes. |
| 1 | Button 2 | Confirm separately; do not infer from the numeric word alone. |
| 2 | Button 3 | Confirm separately before assigning its screen sequence. |
| 4 | Button 4 | The stated mapping uses bit position 4. |
| 8 | Button 5 | The stated mapping uses bit position 8. |
Notice the stated bit positions: the mapping skips positions 3, 5, 6, and 7. Do not “correct” the mapping by assuming button 4 is bit 3 or button 5 is bit 4. Verify each actual key against the monitored word and the HMI configuration. This matters because the screen plan names F1 through F4, while the reported word describes button numbers; verify which word bit corresponds to each physical F key in the actual project.
Check why a key press repeats or disappears
A continuously true button bit is a level, not a single event. If the PLC advances the screen sequence every scan while that bit stays true, holding a key can rapidly step through every screen assigned to it. Conversely, a PLC pulse that lasts only one scan may be too brief for the HMI to detect a requested display change, particularly when a screen takes longer to update.
| Observed behavior | Likely cause | Next check |
|---|---|---|
| One hold rapidly cycles through screens | The PLC logic acts on the sustained button state on repeated scans. | Generate one rising-edge event and advance once per press. |
| A color change sometimes appears and sometimes does not | The PLC changes the display data for only one scan, leaving the HMI too little time to see a stable state. | Hold each state longer; test a 500 ms interval for color cycling. |
| A screen change is missed | The display-change state or trigger may be shorter than the panel’s update time. | Test a stable interval of at least 100 ms, then increase it if the screens are complex. |
| The intended key does nothing | The rung may be watching the wrong bit or a different PLC address from the HMI transfer assignment. | Compare the individual key press with the live button word and transfer configuration. |
Convert each button state into a rising-edge event
Use a positive-differential (rising-edge) operation so the sequence logic receives one event when a button changes from released to pressed. DirectSOFT does not accept a bit-of-word expression such as B2071.1 directly in the STRPD instruction. The practical path is to expose the decoded button condition as a supported bit, then apply the edge instruction to that bit.
The demonstrated ladder pattern is:
STR B2000.0
OUT C0
STRPD C0This is an example of using a bit contact to drive an intermediate control relay and then applying the positive differential to that relay. B2000.0 and C0 are the demonstrated example addresses, not replacements for the project’s actual button bits. Do not substitute them without checking the DL05 address usage and building the required mapping from the HMI button word to the supported bit contact.
- Use the live
V2071reading and the confirmed key mapping to identify each button condition. - Map the relevant condition into a supported bit contact or relay in the PLC program.
- Apply
STRPDto that bit condition, not to the unsupported bit-of-word expression. - Use the one-shot result to increment or select the screen sequence once, and allow the key to be released before another press is recognized.
Route each one-shot to the intended screen sequence
Keep the screen-selection logic in one place in the PLC if the project needs consistent control over screen selection, color, and status-light behavior. The requested mapping is F1 between screens 1 and 3; F2 between screens 2 and 4; F3 between screens 5 and 6; and F4 through screens 7, 8, and 9. Assign each verified key event to its corresponding sequence, and use a separate sequence state for each key group if the operator must retain its position independently.
Define what “cycle through” means for each group before writing the rungs: for example, whether the next press alternates between the two screens, whether a three-screen group wraps from its last screen to its first, and which screen appears on the first press. The intended starting state is not specified by the mapping, so select it explicitly in the project. Then connect the selected PLC state to the configured PLC->Panel screen-change mechanism. The screen-control address and exact C-more configuration are project-dependent; use the existing project’s configured handoff rather than guessing an address.
Stabilize the display command and scan load
Screen and color changes should be held long enough for the HMI to observe them. A one-scan timer or state pulse can be overwritten by the next PLC scan before the panel acts on it. The field guidance for screen updates was to start with at least 100 ms, with the actual requirement depending on screen complexity; for color flashing, 500 ms was suggested as a useful test interval.
Use those values as commissioning starting points, not guaranteed panel specifications. Test on the actual project screens and lengthen the state duration if changes remain intermittent. Also monitor the PLC scan time after adding the logic. Moving display logic into the PLC centralizes the behavior, but additional rungs consume scan time; if the scan time becomes unacceptable, reduce redundant work or reconsider which display functions need PLC-side control.
Restore operation, then verify every key
For a temporary restore, replace continuous level-triggered screen stepping with one-shot processing and hold the requested screen state long enough for the panel to register it. The permanent repair is to confirm the complete transfer mapping, decode each physical key correctly, and test every sequence with normal press-and-release operation.
- With the PLC online, verify the HMI button word changes for one key at a time and returns to its released value.
- Hold each key down. Confirm that it produces only one sequence step rather than repeatedly cycling.
- Release and press again. Confirm that the next one-shot advances the correct F-key group through its assigned screens, including the chosen wrap behavior.
- Test screen changes and any color changes at the configured hold interval. Increase the interval if a transition is missed or inconsistent.
- Monitor PLC scan time and confirm the HMI still receives the required screen and status updates during normal operation.
If the live button word does not match the physical key mapping, stop changing the sequence rungs and correct the panel-to-PLC assignment first. If the transfer is correct but DirectSOFT addressing or the PLC’s supported bit mapping remains unclear, stop and consult official AutomationDirect support or the applicable DL05 and C-more Micro documentation rather than guessing at addresses.
Frequently asked questions
Why does a C-more Micro function key cycle screens while I hold it?
The PLC is likely acting on the button’s sustained bit on every scan. Convert the button condition to a rising-edge event with STRPD so one physical press produces one sequence step.
Why does DirectSOFT reject B2071.1 in STRPD?
The described DirectSOFT use does not accept a bit-of-word expression such as B2071.1 directly in STRPD. Map the button condition to a supported bit contact or relay first, then apply the positive differential to that bit.
Why does the C-more miss a PLC screen or color change?
A state that lasts only one PLC scan may be too brief for the HMI to detect. Test a stable interval of at least 100 ms for screen changes; 500 ms was suggested for color flashing, with screen complexity affecting the result.
When should I stop troubleshooting and call official support?
Stop if the live button word does not correspond to the physical keys after checking the transfer assignment, or if you cannot map the word bits safely in the DL05 program. Escalate to official AutomationDirect support with the HMI transfer settings, monitored PLC values, and relevant ladder rungs.