Troubleshooting ML1000 to C-more Micro DF1 Communication

All four C-more PLC inquiry data tests fail while the MicroLogix 1000 and panel are configured for DF1 Full Duplex at 19200 baud; the reported setup still leaves the PLC parity and checksum settings unverified, and the loopback counts need closer inspection.

Read the PLC inquiry result before changing settings

Record the current configuration and the complete test result first. The panel reports DATA1 through DATA4 as FAIL. That establishes that the inquiry did not complete, but it does not identify whether the cause is driver selection, serial framing, the cable path, or the PLC channel configuration.

The reported settings are:

Device or test	Reported setting/result	What remains to check
MicroLogix 1000 channel	DF1 Full Duplex; 19200 baud; node address 1	Read and record parity, stop bits, checksum, and any other serial-channel settings.
C-more Micro	DF1 Full Duplex; 19200 baud; even parity; 1 stop bit; CRC; direct connection enabled	Confirm the selected driver is specifically for the MicroLogix family and compare all serial settings with the PLC.
C-more inquiry	DATA1–DATA4: fail	Repeat after each single controlled correction; record which tests change.
C-more serial loopback	Reports sent-byte and error-count fields; RTS/CTS fail	Record exact counts and identify which port and test wiring were used.

Do not use the inquiry failure alone to justify changing baud rate: both devices are reported at 19200 baud. Move to driver selection, then compare the complete channel parameters.

Select the MicroLogix-specific DF1 driver

A DF1 label alone is not enough. The C-more driver list may offer separate DF1 drivers for MicroLogix, SLC, and PLC-5 families. Select the MicroLogix driver for the MicroLogix 1000 rather than a driver chosen only because it also says DF1. A family-specific driver determines how the panel addresses and exchanges data with the controller; a wrong selection can prevent a valid inquiry even when the serial cable and baud rate are correct.

1. Open the C-more project’s PLC or device driver configuration.
2. Read the complete driver name and confirm that it identifies the MicroLogix family.
3. Download or apply the corrected project configuration using the normal panel workflow, then rerun the PLC inquiry.

If the inquiry changes from all four data tests failing to a response, retain that configuration and proceed to a simple read test. If it still fails, do not cycle through unrelated drivers; continue with the serial parameter comparison.

Compare every DF1 serial setting at both ends

Baud rate is only one part of asynchronous serial framing. The panel is reported as even parity, one stop bit, and CRC checksum. The PLC report gives DF1 Full Duplex, 19200 baud, and node address 1, but does not state its parity, stop-bit, or checksum values. Read those values in the PLC channel configuration and make the panel’s communication settings match the controller’s actual settings.

1. In RSLogix 500, inspect the MicroLogix 1000 channel configuration and record the complete DF1 serial configuration.
2. In the C-more device configuration, compare driver family, baud rate, parity, stop bits, checksum type, and connection mode against the PLC values.
3. Confirm the PLC node address is 1 and inspect the panel’s target-address field. Do not mistake DEV001 for the PLC address without checking what that field represents in the C-more configuration.
4. Change one mismatch at a time, apply the configuration, and rerun the inquiry. Keep a before-and-after record.

The reported baud rates already agree at 19200. The known comparison requiring attention is parity: the panel is set to even, while the PLC parity has not been reported. Also verify CRC at the PLC; matching baud does not compensate for a parity or checksum mismatch. The panel is set to direct connection, so confirm that this mode matches the actual point-to-point wiring arrangement rather than a network or modem path.

Inspect the communication cable and connection path

The setup uses a C-more communication cable connected to the MicroLogix 1000, but the cable’s exact part number and wiring are not stated. A cable that fits the connector can still have the wrong pinout, signal routing, or handshake conductors. Check the cable against the connection requirements for the selected panel driver and controller; do not assume a cable is correct solely because it is described as a C-more cable.

1. With the equipment safely de-energized as required by the installation procedure, inspect both connectors, cable seating, pin damage, and strain damage.
2. Verify the cable’s part number and pinout from the product documentation available on site; the discussion mentioned EA-MLOGIX-CBL as a candidate, not as a confirmed cable used in this installation.
3. Check for an unintended adapter, terminal block, or intermediate connection that could interrupt transmit, receive, common, or handshake signals.
4. Reconnect the documented cable directly, then rerun the inquiry without changing the PLC or panel serial parameters.

If correcting the cable path changes the inquiry result, treat that as a cable or connection issue and inspect the removed cable before returning it to service. If no documented cable/pinout is available or connector wiring is uncertain, stop cable substitutions and obtain the official wiring documentation for the exact panel and controller.

Use loopback results to separate panel faults from PLC faults

A serial-port loopback test checks a local transmit-and-receive path; it does not prove that the controller driver, PLC address, or DF1 settings are correct. The reported test lists sent-byte and error-count fields for serial ports 1 and 2, and an RTS/CTS failure, but it does not provide the numerical counts or enough detail to determine whether the loopback passed.

Repeat the panel’s documented loopback procedure separately on each port, using only the specified loopback connection. Record bytes sent, error count, RTS/CTS status, port number, and the exact connection used. Interpret the outcome this way:

Observation	Next decision
Loopback passes on a port	The tested local transmit/receive path works under that test setup. Continue with the PLC driver, framing, address, and cable checks.
Loopback fails on one port only	Repeat with the documented test connection on that port and compare the other port. Suspect a port-specific connection or hardware issue if the result repeats.
Loopback fails on both ports	Verify the loopback method and connection first. If the documented method is correct and both ports still fail, isolate the panel from the PLC cable and contact official C-more support.
RTS/CTS fails	Check whether the chosen loopback method and cable are expected to exercise hardware handshake signals. Do not infer a PLC protocol failure from this indicator alone.

Reduce the first data test to one known PLC address

After inquiry succeeds, test one simple data item before restoring a full screen or tag list. The suggested starting address is N7:0. Confirm in the RSLogix 500 project that this address exists and is appropriate to read in the running program; use the correct data type and read operation in the C-more object.

1. Create one display object that reads only N7:0.
2. Run the panel and compare the displayed value with the corresponding value in RSLogix 500 while both systems are online.
3. If the inquiry passes but the value does not, check the exact address syntax, data type, and panel object configuration before altering the serial layer.
4. If the single read works, add the remaining tags in small groups and retest after each group.

A minimal read separates transport from tag configuration. If inquiry remains failed, tag edits cannot repair the serial connection; return to the driver, parameter, and cable decision path instead.

Restore production with a controlled configuration and verify it

For a temporary restore, return to the last known-good cable and recorded settings, then apply only the correction demonstrated to change the inquiry or read test. Avoid simultaneous changes to driver, baud, parity, checksum, and wiring; that may restore communication without identifying the failed condition.

1. Save a copy of the current PLC and C-more configurations before editing.
2. Apply the specific correction: MicroLogix driver selection, matched serial parameters, corrected documented cable path, or panel-port repair as indicated by the checks.
3. Verify that the PLC inquiry completes, then verify a read of N7:0 against RSLogix 500.
4. Restore the required screen tags in stages and confirm stable values during normal operation.
5. Record the final driver, PLC channel parameters, panel parameters, cable part number, inquiry result, and tag test result for permanent repair documentation.

Keep a temporary cable or configuration substitution clearly identified and replace it with the documented, compatible component during permanent repair. Stop testing and contact official Allen-Bradley or C-more support if the documented driver and matching settings still fail, if loopback repeatedly fails with the correct test setup, or if the cable pinout cannot be verified.

Frequently asked questions