An F key keeps changing screens until a control takes it over. Bind the key on the left side of the button definition window, in the Function Key Assign dropdown, F1 through F10, then set a pushbutton to toggle your bit: F1 flips C35 on every press and holds the state.
An F key on a C-more panel keeps changing the screen because a screen change is still its job. To make F1 toggle memory bit C35, put a pushbutton on the screen and open its definition window. Use the Function Key Assign dropdown on the left side to bind the control to F1. Set the pushbutton's action to toggle and enter C35 as the address. The key then flips that bit on every press.
The Function window is the wrong window for this. The binding belongs to the button object, and any control that acts on a single button push can take one of the 10 key choices, F1 through F10. The steps below follow a 3-inch C-more Micro panel and one bit, and they hold for any key and any single-push control.
How do I use C-more F keys for more than changing screens?
Link the key to a control that acts on one button push. Any such control can be bound to a specific F key from the left side of its definition window. Once a pushbutton owns F1, the key stops being a page turner and fires that pushbutton instead.
The page change you see is the key's current assignment, and it goes away when the binding moves to a control. Keys are not fixed to page turns. Every control that acts on a single button push carries an F-key assignment in its definition window, on the left side, and the dropdown there runs F1 through F10. Pick the control first, then the key.
What you need before the steps: the programming software on a PC with the project open, the address of the bit you want to flip, and either the panel on its programming cable or the simulator for a first pass. The whole edit and test fits in under 15 minutes on the simulator.
Why can't I find the F-key setting in the Function window?
You were in the window that owns the page-change behavior. The key binding for a control lives in that control's definition window, on its left side, where the Function Key Assign dropdown lists 10 choices, F1 through F10. That dropdown is where this link is made.
The Function window is where the screen-level functions sit, which is why a key configured there turns pages. A toggle on C35 is a control action, so it is configured on the control. If the key still pages after you bind the pushbutton, one of two things is true. Either the pushbutton never received F1 in its own definition window, or an older screen-change assignment still points at F1. Check the pushbutton first, then hunt the old assignment. Both checks are quick, and both live in definition windows, not in the Function window.
Which controls can an F key trigger?
Any control that acts on a single button push. The pushbutton switch, the radio button and the key button all qualify, and each takes its key from the same Function Key Assign dropdown. Controls that need a sequence of touches or a held press have no key to borrow.
| Object | Acts on one push | Fit for the F-key toggle |
|---|---|---|
| Pushbutton switch | Yes | The natural home: set its action to toggle and bind the key. |
| Radio button | Yes | Selecting one option in a group with a key press. |
| Key button | Yes | On-screen keypad keys; the object is built for that job. |
| Screen-change function | No object action | What the key does until a control takes it over. |
For the C35 toggle, use the pushbutton switch. It is the object built to write a bit on a push, and one flip per press is exactly its toggle behavior. The key button earns its place when you are building an on-screen keypad, and the radio button when one key should pick one option out of a set.
Example: F1 toggles C35 on a 3-inch panel
The example uses a 3-inch C-more Micro panel, whose keypad carries 5 physical keys, F1 through F5. The dropdown offers 10 choices, so 10 minus 5 leaves 5 assignments with no key to press on this panel. The safe keys here are F1 through F5.
The target is the memory bit C35, and the test starts with the bit at 0. Each press takes under 1 second, so the 8-press ledger below runs in under 10 seconds on the bench:
| Presses on F1 | C35 |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 0 |
| 3 | 1 |
| 7 | 1 |
| 8 | 0 |
After n presses the bit is n modulo 2, so 7 mod 2 = 1 and 8 mod 2 = 0. An odd count of presses leaves the bit on; an even count leaves it off. Every press must also leave the screen number alone. Put an indicator object beside the pushbutton so the state is visible without going online in the controller.
How do I set F1 to toggle memory bit C35?
Create or select a pushbutton, bind it to F1 in its definition window, and point its write action at C35 with the toggle behavior. Every press flips the bit and the state holds after you let go. The whole edit is one window and one dropdown.
- Open the project in the programming software and go to the screen that will carry the control.
- Place a pushbutton switch object on that screen, or select the one already doing the job.
- Open its definition window. The F-key field sits on the left side.
- In the Function Key Assign dropdown, choose F1. The list runs F1 through F10.
- Set the pushbutton's write action to toggle, and enter C35 as the address. Each press flips the bit once, and the state holds after the key is released.
- Take F1 off its old job. If the key changed screens before, that screen-change assignment still points at F1; open it and clear it so the key carries one duty.
- Save, then transfer the project to the panel. The choice between the D2-DSCBL serial cable and USB for programming is a separate decision worth settling before you transfer.
How do I check the toggle works on the panel?
Press F1 twice and watch the bit. The first press takes C35 from 0 to 1 and the second takes it back to 0. Neither press may move the screen. If you would sooner keep the machine out of it, run the same 2 presses in the simulator first.
Start in software. Testing C-more Micro function keys in the simulator covers exactly this pass, and it catches a key bound to the wrong control before anyone stands in front of the machine.
Then transfer and press on the panel:
- Press F1 once: C35 goes 0 to 1.
- Press F1 again: C35 returns to 0.
- Confirm the screen number never changed on either press.
- Confirm F2 through F5 still run their own jobs, so the edit took only the key you touched.
- Watch C35 in the controller's online view, or on the indicator from the example above.
If C35 feeds motion or heat, make those 2 presses with the outputs in a state where a surprise write cannot move anything. The working habit is operator panel link setup that tests writes before motion, and it applies to one key as much as to a whole screen.
When should the toggle live in the PLC instead of the panel?
When anything besides the operator writes that same bit. Two writers on one address give you a switch that flips on its own, so keep the panel side to reporting the key press and do the flip in ladder, where you can see it.
The panel keeps a status bit for each function key, and those bits can be read and written between the panel and the PLC. So bind nothing to the key: leave it a plain key, let ladder see its status bit go to 1 on the press, one-shot the transition, and flip C35 in program. Two writers announce themselves exactly as in an HMI switch that mirrors a PLC bit and toggles by itself: the bit changes with no key press. If your line ever does that, count the writers before you blame the panel.
When ladder watches the key's status bit, read the case of a function key bit that stays on after a short press first, because the one-shot belongs on the press transition and how long the status bit holds changes what the rung sees. For the ladder side, a double-action push button PLC toggle with OSR and ONS walks the same flip through one-shot instructions.
Recommendation: bind F1 in the pushbutton's definition window and toggle on the panel when the operator is the only writer of the bit, as with a lone memory bit like C35 driving an indicator. The moment the program also writes the same address, leave the key as a status input to the PLC and do the flip in ladder with a one-shot.
Questions
What is the difference between a toggle and a momentary action on an F key?
A momentary action makes the bit follow the key: C35 is 1 while F1 is held and drops to 0 when you release it. A toggle flips the bit on each press and leaves it, so one press turns the bit on and the next turns it off. Pick toggle whenever the state must outlive the key release.
Can I toggle a bit other than C35?
Yes. C35 is only this example's address. Open the same pushbutton definition and enter any valid bit address in its action field. Point the control at a bit the ladder does not also write; when the program needs to write the same address, do the flip in the PLC and let the key report the press instead.
Should two controls share one F key?
No. Give each control its own key so one press always has one meaning. The dropdown lists 10 choices, F1 through F10, and a 3-inch panel carries 5 keys, F1 through F5, so plan around the keys the operator can actually reach and put screen changes on the ones you can spare.
Does the toggle survive a power cut?
The panel writes the bit; it does not store it. C35 lives in the controller, so what survives a power cut is a property of that controller's retentive memory, and the panel shows whatever the bit reads after startup. Check the retentive range in the controller before you hang anything on the key that must hold through a restart.
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