A panel that talks to a CLICK PLC on port 1 but returns address-not-the-same or different-function-code errors on port 2 is still configured for port 1's interface. Set Select RS485 to Yes in Panel Manager, enter port 2's Com Port Setup values in the panel's device connection, then retest with a known read and a controlled write.
Move an HMI panel from port 1 of a CLICK PLC (a C0-02DR-D, for example) to port 2 and the same project starts failing: the panel reports "address not the same", or that the PLC sent back a different function code, and writes never reach the PLC. The project is still set up for port 1. Two edits fix it, and both use screens you already have: in the panel's configuration software, Panel Manager, set Select RS485 from No to Yes for the CLICK connection, then copy port 2's values out of the CLICK's Com Port Setup into the panel's device connection. Port 1 needs neither edit, because the CLICK serial setup documentation gives 38400 baud as the value for a panel on port 1, which is why the port 1 connection works untouched.
What each symptom points to
Each CLICK serial port holds its own communication configuration, so a fault that appears the moment the cable moves lives in that port's settings, its wiring, or the interface the panel selects.
- Works on port 1, dead on port 2. The panel connection is still set for port 1's interface. The documented switch is Panel Manager's Select RS485, set from No to Yes for a port 2 connection.
- "Address not the same." The station address in the panel's device connection and the address port 2 answers on disagree. With the wrong interface selected, port 2 produces the same error, so fix the interface first and match the address second.
- "PLC sent back different function code." The reply does not match what the request expects, which is what traffic looks like when a port's interface or serial settings are wrong. Treat it as a port 2 settings problem before touching the PLC program.
- Reads work, writes fail. The link is up and the fault has moved to the write target: the panel object's write address, or PLC logic guarding that location.
- Both ports fail. The cause sits outside the port settings: the cable, the panel project or the power feed.
Check that the failure follows the port
Keep the panel project unchanged while you collect evidence; this is diagnosis, not tuning.
- On port 1, run a known read and a controlled write, and record that both work.
- Write down the panel connection's current values, so any test change can be reversed.
- Move the panel wiring to port 2 and repeat the same read and write. Record the exact error text.
- If port 1 also fails, stop there: the cause is common to both ports, so check the cable, the power feed and the panel project before editing port 2 at all.
Read port 2's values in the CLICK
Open the CLICK Programming software, choose the Setup menu, then Com Port Setup, and select Com Port 2. Write down every field that screen shows: the Baud Rate field, parity, data bits, stop bits and the station address for that port. The CLICK serial setup page in the panel's help states the baud rule plainly: the panel's value must match the Baud Rate field for the PLC port in use, and a panel on port 1 should be set to 38400. Port 2 carries whatever your project sets, so read the screen instead of letting port 1's numbers carry over in your head.
Compare the two ends field by field. One wrong field is enough to kill the link, and a single mismatched serial setting produces a recognizable failure; the article on HMI serial errors from a PLC parity mismatch shows what one looks like.
Set Select RS485 to Yes and match port 2
Port 2 on the CLICK is the RS-485 port, and the panel must be told to drive that interface; that is the entire job of Select RS485.
- Open the panel project in Panel Manager and find the CLICK device connection.
- Set Select RS485 from No to Yes.
- Enter the values you wrote down from Com Port Setup: baud, parity, data bits, stop bits and station address. Every field must agree with port 2's entry in the CLICK project.
- Save and transfer the project to the panel.
- Rewire to port 2's terminals on the CLICK CPU. RS-485 is a differential pair, so keep the pair's polarity consistent end to end; the CLICK manual's wiring chapter shows the terminals. For a long run, plan against the interface standards' figures, about 15 m for RS-232 and about 1200 m for RS-485 at low baud rates; the serial cable maximum distance by interface article lists the details.
- Power both units and test a known read first, then a controlled write.
If Select RS485 already reads Yes, leave it where it is and recheck the selected device connection, the CLICK's port 2 screen and the physical wiring. Toggling the same setting repeatedly hides the real fault.
Building the port 2 connection from scratch instead of moving a working one? The fixed serial settings walkthrough covers both ends in order.
Example scenario: moving a working panel from port 1 to port 2
These numbers show the whole move on one CLICK CPU. Port 1 works today and the panel connection carries 38400 baud, the documented value for a panel on that port. Com Port Setup shows port 2 as follows; these are example values, so read your own screen and keep your own numbers, because the comparison is the point. 19200 appears here because the CLICK's serial examples use it on a controller port, so it is a value a CLICK port really carries.
| Setting | Port 2 in the CLICK (example) | Panel before the move | Panel after the edit |
|---|---|---|---|
| Baud Rate | 19200 | 38400 | 19200 |
| Parity | even | even | even |
| Data bits | 8 | 8 | 8 |
| Stop bits | 1 | 1 | 1 |
| Station address | 1 | 1 | 1 |
| Select RS485 | Yes (RS-485 interface) | No | Yes |
Work through the comparison field by field, before the edit. Baud Rate: 38400 on the panel against 19200 in the CLICK, 1 mismatch. Parity: even against even, agree. Data bits: 8 against 8, agree. Stop bits: 1 against 1, agree. Station address: 1 against 1, agree. Select RS485: No on the panel against the RS-485 interface port 2 requires, 1 mismatch. Total: 2 of 6 fields disagree. That state produces the address and function-code errors even though every serial value on the panel's screen looks matched, because the baud is off by 19200 (38400 minus 19200) and the interface selection is wrong.
Now apply the two edits and count again. Baud Rate becomes 19200, matching the CLICK: agree. Select RS485 becomes Yes, matching port 2's interface: agree. The other 4 fields were already equal and stay equal. Total after the edit: 0 of 6 fields disagree. With 6 of 6 fields in agreement, the tests decide the result: a read returns the expected value from the CLICK, and a controlled write to a spare register changes that register's value in the PLC. The move is finished when both directions pass on port 2.
If reads work but writes still fail
After Select RS485 is Yes and port 2's values match, writes ride the same link as reads; the port 2 no-write complaint goes away with the interface fix. If a read now succeeds and a write still fails, the fault is in the write target: check the write address on the panel object, then any PLC logic that guards that location.
Safety note: run the write test on a spare register that drives nothing. A write to the wrong word can start a motor or move a machine.
| Result on port 2 | What it tells you | Next check |
|---|---|---|
| Read and write both work | Interface and settings support both directions | Put the connection back into normal operation and watch one cycle |
| Neither works | The port 2 link is still down | Recheck Select RS485, the Com Port Setup values, the station address and the wiring |
| Reads work, writes fail | The link is up; the write target is at fault | Check the object's write address and the logic guarding that location |
| Address or function-code error remains | Request and reply still disagree | Compare the device selection, the interface and every port 2 field again, and record the exact error |
A working read does not confirm the write path, which is why the write test to an approved location is part of the job.
The decision
Recommendation: When a panel moves from CLICK port 1 to port 2, make both edits in one pass. Set Panel Manager's Select RS485 to Yes for the CLICK connection, copy every Com Port Setup field from port 2, including the station address, into the panel's device connection, rewire to port 2's terminals, then test a known read and a controlled write to a spare register. If reads work and a write still fails, fix the write object's address or the logic guarding it; no port setting will help. Record the final Select RS485 value and port 2's settings with the project backup, and treat a move back to port 1 as a temporary restore only.
Questions
Do I need to change anything in the CLICK project to use port 2?
Only if its values are not what you want. Port 2 is configured in the CLICK Programming software under the Setup menu, Com Port Setup, Com Port 2, the same screen that shows the values the panel must match. Changing port 2's baud, parity or station address there leaves port 1 alone, so whatever runs on port 1 keeps working. Read the values back after saving, then enter them in the panel's device connection.
Why does the panel report an address error when every setting looks the same?
Because the panel can carry matching serial values and still select port 1's interface, with Select RS485 still reading No. On the wrong interface, request and reply never line up on port 2, so the panel reports address not the same or a different function code. Set Select RS485 to Yes, then verify the station address in the panel's device connection against port 2's setting in the CLICK.
What should I record once port 2 works?
Save both projects and note three things: the Select RS485 value, Yes, in Panel Manager; every Com Port Setup field for port 2; and the spare register used for the write test. With that record, the next project edit or panel swap can be checked against known-good values in minutes. Moving the panel back to port 1 recovers communication for the moment but leaves port 2 unconfigured, so keep the working port 2 setup as the reference.
Planning information, not legal or engineering advice. Rules differ by place: check codes and permits with your local authority and your licensed trades.