Display CLICK PLC time on an HMI panel screen

Where the CLICK PLC stores the clock

The clock occupies seven system data registers, SD20 through SD26. Each field is its own integer, so the panel assembles the clock from three separate reads instead of one ready-made time string.

SD20 stores the year as 2 digits. SD26 holds the current second, which runs from 0 to 59. The other fields hold the plain integers their names say, and the date fields feed the same method if the layout also wants a date line.

Check the CPU part number first

Read the full part number from the CPU label or from the hardware configuration in the CLICK programming software. It begins with C0-00, C0-01 or C0-02. Only the C0-01 and C0-02 families carry the real-time clock, and within those families every CPU has it; the part numbers in a family differ in their input and output mix. A C0-00 has no real-time clock, so SD24, SD25 and SD26 hold nothing current and the panel has no time to print.

Recommendation: check the part number before you open the screen editor. If it starts with C0-01 or C0-02, build the clock from numeric display objects tagged SD24, SD25 and SD26, set a colon suffix on the hour and minute objects, and switch on leading zeros for minutes and seconds. If it starts with C0-00, stop the register approach: move to a C0-01 or C0-02 CPU, or drive the clock fields from a time source your controls design already keeps accurate.

What you need

• The checked CPU part number: C0-01 or C0-02.
• The panel project open in its programming software.
• A CPU clock that is actually set. If it has never been set, setting the PLC clock from the operator panel covers that job and the daylight-saving change.
• The transfer path you already use to download a project to the panel.

Build the clock on the screen

Work down the steps in order. Each one sets up the next.

1. Re-read the CPU part number on the label or in the project hardware configuration. C0-01 or C0-02: continue. C0-00: stop and change the plan as above.
2. Set the CPU clock if it has never been set. The panel repeats whatever the CPU holds, so a wrong clock prints a wrong clock.
3. Add a numeric display object and give it a tag addressed to SD24, the hour. In this driver the tag address is the register name itself.
4. Add two more numeric display objects, tagged SD25 and SD26. Sit them side by side in the order hour, minute, second, close enough to read as one line.
5. Set the object suffix to a colon on the hour object and again on the minute object. Leave the second object without a suffix.
6. Turn on the leading-zeros option for the minute and second objects. Type no zero into a label as a substitute: a fixed 0 stays on screen when the register reaches 10, and a 10 prints as 010.
7. Download the project by your normal transfer procedure, with the PLC running.

The field-per-object build is the same one behind displaying HH:MM:SS time on an HMI numeric object; this job only binds it to the CLICK register names. The leading zeros on a split HMI numeric display article goes deeper on the option itself.

Worked example: a C0-01 CPU holding 14 h 07 min 09 s

The CPU part number starts with C0-01, so the clock is present. Mid afternoon on a 24-hour line, the registers hold SD24 = 14 hours, SD25 = 7 minutes, SD26 = 9 seconds. The values are ordinary register contents: the second field runs 0 to 59, so 7 and 9 turn up every minute.

The rule in words: a numeric display object prints the integer in its register and appends its suffix after the value. Leading-zero formatting pads any value below 10 to two characters.

The arithmetic:

• Minute: 7 < 10, so the field prints 07.
• Second: 9 < 10, so the field prints 09.
• Hour: 14 already carries two characters, so nothing pads.
• Hour object with its colon suffix: 14:. Minute object with its colon suffix: 07:. Second object with no suffix: 09.

Side by side, the line reads 14:07:09 and holds its width through the whole minute. With leading zeros off, the same registers print 14:7:9, and the line changes width every time a field crosses 9, as at 09 to 10.

The decision the numbers give: switch leading zeros on for every field that spends time below 10. A minute or second takes each value from 0 to 59, so 10 of its 60 values print single-digit, one count in six. That is why the option goes on those two objects. The colon suffix goes on the two objects that have a field after them, never on the last one, or the line ends in a stray colon.

How to check it worked

Stand at the panel with a clock you trust, with the PLC running.

• Watch one minute boundary. The second object must step 57, 58, 59, 00 and keep two characters from 00 through 09.
• Read the hour and minute against the trusted clock; they must agree within the time it takes to look.
• Check the field width held steady across 09 to 10.

One commissioning rule: leave the screen out of operator use until its fields have tracked the running PLC through a minute boundary. Operators read a plant clock and act on it.

If a field sits at 0 or freezes, work down the layers in order, because each check rules out a different one:

1. The part number. A C0-00 has no clock, and no screen work recovers it.
2. The tag addresses. Each tag must name SD24, SD25 or SD26 exactly.
3. The communication state on the tags. A faulted tag prints nothing useful.
4. The formatting. A suffix on the wrong object or leading zeros left off change how a value prints, never what the tag reads.

Formatting is the last stop for a reason: suffixes and leading zeros shape the display, and they never supply time or repair an address.

Questions