Copy the MicroLogix 1200 long value into a pair of N-file words, then configure the C-more tag as a signed 32-bit integer; a single 16-bit N register cannot hold the full value. If the installed C-more software offers direct L-file addressing, use its documented driver support instead of maintaining a duplicate value.
Check whether the installed C-more software supports L-file tags
The reported limitation was that the C-more tag configuration did not offer the MicroLogix 1200 L data file. A later software revision was expected to add L-file provision, but that historical expectation does not establish what a currently installed version supports. Check the installed software's available tag data types and the current device-driver documentation before changing the PLC program.
- Record the C-more software version and the selected PLC driver.
- Inspect the tag configuration for a supported 32-bit L-file type.
- If the type is available, confirm its addressing and signedness in the driver documentation, then test a known value.
- If it is unavailable, use the N-file workaround below.
Do not select a 16-bit tag and expect it to read an L value without truncation or conversion. Proceed only after confirming which data type the panel can actually read.
Reserve two N-file words for each long value
An N-file element is 16 bits; it cannot independently represent the complete 32-bit value. The workaround described for this pairing is to expose the PLC's long value through two N-file words and configure the HMI to interpret those words together as one signed 32-bit integer. Reserve two consecutive N elements per value and keep their purpose documented so other logic does not overwrite them.
Choose a source L element and a destination pair, for example, an L-file value and two reserved N-file elements. The example is conceptual: use addresses and instruction forms valid for the actual MicroLogix 1200 program and programming software. Check that the source range fits the signed 32-bit representation selected for the display.
Check: identify the source long value, its meaning and valid range, and the exact two N-file elements dedicated to its display copy.
Copy the long value without changing its representation
Implement a PLC-side copy or conversion that places the complete 32-bit value across the reserved pair. A simple move into one 16-bit N element loses information; two independent conversions can also produce an incorrect combined number. Use a PLC instruction or method that preserves the source's 32-bit bit pattern across the two words, and confirm its operand-width behavior in the programming environment's instruction help.
Keep the source and destination interpretation aligned. If the source is signed, the HMI's signed 32-bit interpretation must match. If the application uses unsigned values, do not display them as signed without checking the consequences: values with the high bit set can appear negative under signed interpretation.
When the source can change while the PLC copies the two words, the HMI could briefly read one word from the previous value and one from the new value. If that transient matters to the process, use a copy/update strategy that the PLC and panel can consume consistently, such as publishing a stable snapshot only after both words are updated. Choose the implementation based on the PLC's available instructions and the panel's read behavior; do not assume a two-word read is atomic.
Check: monitor both N words in the PLC and confirm they change from the chosen source through the selected 32-bit-preserving method.
Configure the C-more tag as Signed Int 32
In the C-more project, create a tag using the PLC's N-file address corresponding to the first word of the reserved pair, and select the signed 32-bit data type described for the workaround. The panel must treat the two 16-bit values as one 32-bit value; assigning a 16-bit type or pointing at an unrelated word will not produce the intended result.
Check the driver's documented word ordering. If the displayed number is wrong even though both N words look correct, the HMI and PLC may interpret the low-order and high-order words in opposite order. Correct the mapping or use a PLC-side arrangement supported by the driver, then recheck positive and negative test values. Do not compensate by swapping words blindly; verify the actual interpretation.
Check: confirm the configured tag's address, signed 32-bit type, and documented word order before downloading the project or relying on the display.
Verify the displayed value across the full operating range
- Test a value whose 32-bit representation requires more than 16 bits; confirm the panel shows the same value as the PLC source.
- Test zero and, if the application uses signed values, a negative value. Compare the source, both N words, and the displayed result.
- Change the source while observing the display. Check for stale, truncated, sign-reversed, or briefly inconsistent readings.
- Repeat the comparison after a panel or PLC restart to confirm the copy logic runs and the display recovers as intended.
If the panel shows only a small value, first check whether the tag is configured as 16-bit. If it shows the wrong large value, check word order and the PLC copy method. If the sign is wrong, check signed versus unsigned interpretation. Change one factor at a time and compare the PLC source, destination words, and HMI result.
FAQ: C-more and MicroLogix 1200 32-bit tags
What happens if I copy an L value into one N register?
The N element holds only 16 bits, so one element cannot carry the complete 32-bit value. Use a reserved pair and configure the panel to interpret them together as signed 32-bit data.
What happens if the C-more display shows the wrong large number?
Compare the PLC source with both N words, then check the driver's word order and the PLC's copy method. Do not swap words until the documented or tested ordering identifies the mismatch.
What happens if a positive value appears negative?
Check whether the value exceeds the signed 32-bit range or whether the HMI tag's signed interpretation differs from the PLC value's intended interpretation. Confirm the application's range before changing the data type.
What happens if my C-more version offers L-file addressing?
Use direct L-file addressing only after the installed driver's documentation confirms the supported type, address format, and signedness. Verify it against known PLC values before removing the N-file workaround.
Stop before deploying if the driver's word order or the PLC copy method remains unclear, or if testing shows inconsistent values that could affect an operator decision. Consult AutomationDirect's official support channel and provide the panel software version, selected PLC driver, tag type, and PLC-side source/destination values.