EZ-S6M-R Startup Clears Discrete Tags: Find the Cause

The EZ-S6M-R clears the touchscreen-linked discrete selections at startup in this installation, while untouched discrete addresses and integer addresses remain unchanged. Treat that pattern as an HMI startup write until a controlled test proves the PLC’s retentive configuration is clearing the bits; restore the schedule from retained PLC data if the panel offers no setting to preserve those selections.

Compare one affected bit with one untouched bit

Before changing ranges or rewriting the program, identify one discrete address linked to a calendar selection and one discrete address that the EZ-S6M-R does not use. Record each value before power-down, then read both at the PLC after power returns and before the operator touches the screen. Also record one integer value as a control. The reported pattern is that linked discrete addresses go off, untouched discrete addresses do not, and integer addresses remain unchanged.

Use PLC online monitoring or another read-only method for the comparison. Do not test with a bit that directly starts equipment: a retained or restored command bit can create an unexpected start condition. Calendar selections are configuration data, but verify that the PLC program treats them as schedule inputs rather than as direct output commands.

Check the PLC retention range for the linked address

On a DirectSoft-controlled DL06, inspect PLC > Setup > Retentive Ranges and compare the range against the actual C addresses linked to the screen. The cited default is C0-C999 nonretentive and C1000-C1777 retentive. Those ranges are specific to the DL06 default described here; read the actual configuration in the installed controller rather than assuming the default is still active.

1. Record the exact C address for an affected screen object and a nearby unaffected bit.
2. Open the controller’s retentive-range setup and determine whether each address is configured to retain state through power loss.
3. Compare the result with the PLC value after power returns, before changing the touchscreen or program.
4. If the schedule bits fall in a nonretentive range, select an approved range or remap the HMI tags to retentive addresses, then test the full affected schedule.

The historical diagnosis proposed that the EZ-Touch tags might be in C0-C999. That is a testable explanation, not proof that every cleared bit has this cause. The observation that untouched bits are unaffected makes it especially important to inspect exact tag addresses and distinguish PLC retention from an HMI write.

The report also names an SLC 5/05 and says its memory survived a one-minute power interruption with a good battery, yet the linked bits still cleared. That observation argues against a simple loss of all PLC memory, but it does not establish the SLC’s retention configuration or exclude a tag-specific write. Check the SLC’s actual data file and program behavior independently; do not apply DL06 C-range defaults to an SLC 5/05.

Isolate whether the touchscreen writes zero at startup

Retentive PLC memory preserves a PLC value across loss of power; it does not prevent a connected HMI from subsequently writing a different value. A screen object linked to a discrete PLC tag can therefore show or send an off state during panel startup while unrelated addresses remain unchanged. An integer object or integer tag may follow a different initialization and write path, so unchanged integers do not prove that the discrete tags are being retained correctly.

1. Monitor an affected PLC bit online and record its value before cycling the panel.
2. If the test can be done safely, restart only the HMI while leaving the PLC powered, and monitor the bit continuously from before panel startup through screen initialization.
3. Compare the moment the bit changes with the HMI’s communication return and screen display. A transition coincident with panel startup points toward HMI tag/object startup behavior; a transition when the PLC alone restarts points toward PLC retention or startup logic.
4. Review the configured tag address and object type for a calendar selection. Confirm that the panel object writes the intended PLC bit rather than another address.

If the installation cannot safely separate panel and PLC power, do not improvise a live test on a running machine. Use a safe maintenance state and capture PLC values before and after a controlled restart. The prior operator inspection found no accessible EZ-Touch control that prevented the discrete addresses from being cleared; check the installed project and panel configuration before concluding there is no applicable setting in the version at hand.

Keep calendar selections separate from start commands

The calendar represents operator-selected days for a chemical-addition schedule. It is not the same function as a momentary pushbutton that issues a motor start. Clearing a bit on startup can be a reasonable fail-safe choice for a start command because a machine should not restart merely because an old command remains set. Applying that same policy to retained scheduling data, however, discards operator configuration and forces schedule re-entry after a service outage.

Classify each HMI-linked bit by purpose before choosing a retention fix:

• Configuration state: A calendar-day selection or similar machine parameter may need retention so the schedule survives a power cycle.
• Command state: A start request or other action command may need to clear on startup to prevent unintended operation.
• Derived or transient state: A bit recalculated by PLC logic should be initialized by that logic, not restored as though it were operator configuration.

Do not make an entire discrete range retentive just to preserve two calendars. Review every address in the affected range and the PLC logic that consumes it. Retaining unrelated command bits can change machine startup behavior.

Choose the least disruptive permanent correction

If the PLC retention setup is the cause, correct the range or remap the schedule tags to addresses configured as retentive. The reported DL06 recommendation offered both choices: use retentive C addresses or adjust the PLC’s range so the used C addresses retain their values. Choose based on the project’s address plan, existing logic, and available retentive memory; update all tag references and any PLC instructions that use the addresses.

If an HMI startup write is the cause and the installed project provides no control to preserve the bit state, use the reported workaround: store the schedule values in PLC registers during normal operation, then copy the recorded values back to the schedule bits after startup. The original approach was to force the recorded values back during roughly the first five seconds after power-up. Treat that interval as a reported implementation, not a universal timing requirement; use the actual panel communication and PLC startup sequence to decide when restoration can safely occur.

Keep the saved schedule separate from temporary command bits. Write the saved values at an appropriate point during normal operation so a sudden outage does not leave the backup stale. Restore only validated calendar data, and prevent the restore logic from overwriting a new operator selection made during startup. If the system has no reliable indication that the HMI has completed communication, determine readiness using the actual project’s available status mechanism rather than guessing a delay.

Apply and verify the schedule restore

1. Back up the PLC program and HMI project. Record the current address mapping and retentive configuration before making changes.
2. Choose one permanent branch: correct PLC retention for the schedule bits, or add a separate saved schedule and controlled startup restore if the panel clears them.
3. Test first with outputs inhibited or in a safe maintenance condition. Select several calendar days, confirm the PLC schedule bits match the selections, and record the saved values if using the restore branch.
4. Cycle power under the test plan and monitor the affected bits, saved data, and displayed calendar. Confirm that the schedule returns as intended and that command bits do not cause equipment to start.
5. Repeat for both 31-discrete screens and verify every linked address, not just the sample points. Check that changing a day after restart updates the schedule and does not get overwritten by stale backup data.

A successful test shows the same intended schedule in the PLC and on the screen after restart, with untouched addresses behaving as expected and no unexpected machine action. Document the selected retention range or restore logic and the test result so the next maintenance outage does not reintroduce the problem.

Stop when the address or startup behavior remains unexplained

Do not expand retentive ranges broadly or force schedule bits back into a live machine when the tag mapping, startup sequence, or bit function is uncertain. Preserve a PLC/HMI project backup and collect the exact addresses, before-and-after PLC values, retention setup, and restart sequence. Stop and contact official AutomationDirect support if controlled testing cannot distinguish PLC retention from HMI startup writes, or if the installed panel configuration behaves differently from the project documentation.

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