Wiring a Wonderware InTouch Pushbutton to Reset Two PLCs

Overview

Many Wonderware InTouch deployments grow to span more than one controller: a Modicon M340 or Quantum handling legacy I/O, an Allen-Bradley CompactLogix running newer EtherNet/IP cells, and a single InTouch HMI that the operator expects to behave as one consolidated front end. The most common operator action that exposes the multi-PLC problem is a global reset: the operator presses one pushbutton, and InTouch must pulse a reset coil in PLC A and a reset bit in PLC B on the same edge.

The technique is straightforward once you understand the three-layer model InTouch uses:

1. An Access Name defines the physical channel to a controller (driver, node, topic).
2. An I/O Discrete tag is the live mirror of a single bit in that controller.
3. A Memory Discrete tag lives entirely inside the HMI and is the right place to land a pushbutton before the script fans it out.

The script is the bridge. When the operator toggles the Memory Discrete, a condition script fires and writes 1 (and then 0) to the I/O Discretes for both PLCs. The PLC ladder accepts the pulse and runs its own reset sequence. This article walks through tag database construction, script logic, PLC-side acknowledgment, and verification on both Modicon and CompactLogix.

Prerequisites

Communication Architecture

Before writing a single tag, you must build two independent Access Names — one for each PLC. InTouch does not multiplex multiple controllers behind a single Access Name; each physical protocol/destination pair needs its own entry under Special → Access Name in WindowMaker.

Access Name 1: Modicon PLC

Access Name 2: Allen-Bradley CompactLogix

Tag Database Configuration

Open the Tagname Dictionary dialog (Special → Tagname Dictionary) and create the following four tags. Names are case-sensitive in InTouch and must match exactly in every script reference.

Modbus bit-addressing conventions for the Modicon coil

Modbus uses zero-based coil numbers:

• Coil 00001 through 09999 are read/write coils (output 0×0 through 0×270E).
• Coil 10001 through 19999 are inputs (read-only).
• Register 40001 through 49999 are holding registers (each 16 bits).

The InTouch MBE/MBTCP driver expects a 5-digit zero-padded number. To pulse a single %M bit in a Modicon M340, the recommended pattern is to expose that %M as part of a %MW word and address the appropriate bit position. A more common and far cleaner pattern is to define the reset as the LSB of a dedicated word:

// In Unity Pro / EcoStruxure Control Expert (Modicon side):
PROGRAM Reset_Logic
  VAR
    HMI_Reset : BOOL;       // mapped to %MW1000.X0 below
    Bypass    : BOOL;
  END_VAR
  IF HMI_Reset THEN
    ResetLatches();          // your reset subroutine
  END_IF;
END_PROGRAM

Then in the I/O Mapping tab of the M340, expose the word %MW1000 with the bit HMI_Reset as %MW1000.X0. The Modbus coil address becomes 00001 (the LSB of 40001 for the first holding register). On the HMI, item 40001 mapped to bit position 0 of the first word is the right call.

Logix tag exposure for the CompactLogix coil

Open Studio 5000 Logix Designer on the L5x file, expand the Controller Tags scope, and ensure HMI_Reset exists with External Access = Read/Write. A typical declaration looks like this:

// Logix tag (Data Type: BOOL, Scope: Controller, External Access: Read/Write)
HMI_Reset : BOOL;    // operator-initiated global reset pulse from InTouch

The InTouch driver takes the Logix tag name verbatim. Do not include the Program: or Controller: prefix. The DASSIDirect AB_ETHIP driver resolves it through CIP symbolic addressing at runtime. If the tag is scoped to a Program, prefix it: Program:MainProgram.HMI_Reset.

Wiring the InTouch Pushbutton

Open WindowMaker and place a pushbutton on the window. The Touch Property of the button is what fires when the operator presses it. Configure it as follows:

1. Select the pushbutton graphic.
2. Open Animation Links → Touch Property → Discrete.
3. Click Tag and bind it to Btn_GlobalReset (the Memory Discrete).
4. Set the action to Toggle if the button is a momentary pushbutton, or to Direct with value 1 and a release back to 0 if the button is a maintained pushbutton. Most operator panels expect Toggle off by default and write 1 on press.
5. Bind the Value Display property to the same Memory Discrete so the operator sees the button change state when pressed.

At this point pressing the button changes only Btn_GlobalReset. The two PLC tags do not move yet. The script is what does the writing.

Condition Script: The Fan-Out

Open Special → Scripts → Condition → On and create a new condition script. A condition script fires on the rising edge of the bound expression, which is what you want for a one-shot reset.

// Condition script: fires when Btn_GlobalReset transitions 0 -> 1
// Author: HMI engineering / project name
// Purpose: pulse reset bits on both PLCs for one scan

IF Btn_GlobalReset == 1 THEN
    MOD_ResetPulse = 1;       // Modicon coil pulse, 1 cycle
    CLX_ResetPulse = 1;       // CompactLogix BOOL pulse, 1 cycle
ELSE
    MOD_ResetPulse = 0;       // back to 0 to avoid latched-on writes
    CLX_ResetPulse = 0;
ENDIF;

Bind the condition script to the Btn_GlobalReset tag. The script runs in the InTouch main loop on every scan, but only takes the write branch when the value is 1. Because the script is a condition script (not an action script on the button itself), it is not debounced by the button event — it follows the state of the Memory Discrete directly.

Edge-detected one-shot (preferred for noisy panels)

If operators can tap the button quickly, use a derived Memory Discrete that fires for exactly one scan. The pattern is:

// In the Quick Script editor as an application script:
// runs every WindowViewer scan (250 ms default)

Btn_GlobalReset_OS = Btn_GlobalReset AND NOT Btn_GlobalReset_Prev;
Btn_GlobalReset_Prev = Btn_GlobalReset;

Then bind the condition script to Btn_GlobalReset_OS instead. This guarantees one pulse per operator press regardless of how long the button is held.

Alternate Method: Button Action Script

If you prefer to keep all reset logic on the button itself, InTouch supports Action scripts bound to a button's Touch Property. An action script runs in the same scan the operator taps, and you can write to any number of tags inside it.

1. Right-click the pushbutton → Animation Links → Touch Property → Action.
2. Set the Action to Discrete → Direct → 1 so the touch sets the button state.
3. Add a script of type On True (script fires when the touch value becomes 1) with the body:

// Action script: fires on button press (touch value = 1)
MOD_ResetPulse = 1;
CLX_ResetPulse = 1;
// let the PLC latch the reset, then drop the pulse from the HMI
DELAY( 200, ResumeLabel );   // wait 200 ms

LABEL ResumeLabel;
MOD_ResetPulse = 0;
CLX_ResetPulse = 0;

The DELAY function yields the InTouch script engine for 200 ms and then resumes at the label. Adjust 200 ms to match the longest PLC scan time across both controllers; for a CompactLogix L33ER with 1 ms task and an M340 with 20 ms MAST task, 100 ms is plenty. Do not exceed 2 000 ms; the InTouch script engine is single-threaded and a long DELAY blocks other animations.

PLC-Side Reset Logic

The HMI pulse is a request, not a command. Each PLC must run its own acknowledge-reset sequence on the rising edge of its respective input. The reasons are: (a) PLC scan time varies, (b) alarms and interlock conditions may legitimately block a reset, (c) the HMI must not assume success.

Modicon M340 / Unity Pro

// Modicon reset routine - structured text
// Trigger: HMI_Reset (mapped to %MW1000.X0 above)

IF HMI_Reset THEN
    IF NOT(Stop_Active) AND NOT(Maintenance_Lockout) THEN
        ResetLatches := TRUE;   // your reset coil
        ResetStatus := 16#0001; // 1 = OK
    ELSE
        ResetStatus := 16#0002; // 2 = refused
    END_IF;
ELSE
    ResetLatches := FALSE;
END_IF;

Allen-Bradley CompactLogix / Studio 5000

// Logix reset routine - ladder or structured text
// Trigger: HMI_Reset (Controller-scope BOOL)

IF HMI_Reset AND NOT(Stop_Active) AND NOT(Maintenance_Lockout) THEN
    ResetLatches := 1;        // your unlatch coil
    ResetStatus := 1;         // 1 = OK
ELSE IF HMI_Reset THEN
    ResetStatus := 2;         // 2 = refused
END_IF;

Expose ResetStatus from each PLC as a Memory integer the HMI can read. Bind it to two new InTouch I/O Integer tags: MOD_ResetStatus and CLX_ResetStatus. The operator panel can then color the reset button green (status = 1), red (status = 2), or grey (status = 0, idle) to confirm the action took effect on both controllers.

Verification & Commissioning

1. Tag browse test. In WindowMaker open Tagname Dictionary, right-click MOD_ResetPulse, choose Read. With the Access Name paused in Offline it should show 0. Switch to Live and force the Modicon coil from Unity Pro — the InTouch value should update within one polling interval.
2. Driver health. Open SMC (System Management Console for the I/O Server) and confirm both Access Names show green status. AN_MODICON_PLC and AN_CLX_PLC must both be in the Active state with no Quality Bad rows in the dabase.
3. Script trace. Open WindowViewer → View → QuickScript Debug and toggle the Memory Discrete manually. The condition script should log MOD_ResetPulse = 1 then MOD_ResetPulse = 0 (and same for CLX_ResetPulse) inside one cycle.
4. PLC forced-edge test. From Studio 5000 / Unity Pro, force MOD_ResetPulse / CLX_ResetPulse to 1 in the InTouch tag and confirm the ladder reacts. Then un-force and confirm it drops to 0 on the next scan.
5. End-to-end button test. Run WindowViewer in Live mode on the HMI node. Press the button. The two ResetStatus integers should both transition to 1 within two polling cycles (worst case 500 ms). If one stays at 0, see the troubleshooting matrix below.
6. Network fault test. Disconnect the cable to PLC B. The button press should still pulse PLC A, and the HMI should display a quality-bad alarm on CLX_ResetPulse. Reconnect and verify the system auto-recovers without restarting WindowViewer.

Troubleshooting Matrix

Security and Best Practices

• Access level. Gate the Btn_GlobalReset tag behind an operator access level that matches the PLC reset privilege. A reset that bypasses interlocks should never be a level-0 button.
• Confirmation dialog. Wrap the button in a confirmation animation. InTouch supports Show Window on a touch release; show a modal that requires a second press within 3 seconds. This prevents accidental resets from a misclick on a touchscreen.
• Audit trail. Add an action script that writes to a Memory Integer log tag every time Btn_GlobalReset fires, and pass that integer to a Historian or AVEVA Insight collector. Resets that bypass interlocks must be traceable.
• Don't fan out from the PLC side. It is tempting to let PLC A's reset trigger PLC B's reset via MSG instructions. Avoid this; it couples the two controllers in ways that are invisible from the HMI. The HMI is the correct place to perform the fan-out because the operator initiated the action.
• Tag naming convention. Use a MOD_ / CLX_ prefix on every I/O tag, and a Btn_ prefix on every operator-initiated Memory Discrete. This makes the script code self-documenting and helps anyone replacing the integrator years later.
• Driver mix. Mixing DASSIDirect and OPC UA on the same HMI is supported but increases the I/O Server's memory footprint. For projects with > 5 000 tags, consolidate to one I/O Server and use AVEVA OI Gateway as a bridge.
• Tag count vs. scan time. An InTouch application with more than 10 000 tags will exceed the default 250 ms scan budget. Increase the WindowViewer priority or split the application into multiple WindowViewer instances running on the same HMI node.

Edge Cases and Field-Proven Caveats

• Redundant HMI pairs. If you run two InTouch nodes in Standby mode with SuiteLink, only the active node has write access to the PLCs. The standby's button presses will appear to do nothing — by design. Verify the active-node tag $SYS_Active before granting reset permission.
• Cybersecurity. Putting PLC reset coils on a routable network exposes them to the operator's IT side. Use a CIP-security enabled CompactLogix (5380 / 5480 series) and confine Modbus TCP to a VLAN that the HMI can reach but the office cannot.
• Modicon M580 vs. M340. M580 supports both Modbus TCP and EtherNet/IP natively. If you have the choice, use EtherNet/IP for the M580 too and skip the Modbus driver entirely; symbolic addressing and signed 32-bit values "just work" on EtherNet/IP but require bit-twiddling on Modbus.
• Firmware drift. After a Studio 5000 upgrade, verify the AB_ETHIP driver on the HMI supports the new firmware revision. A mismatch can leave the Access Name green in SMC but unable to resolve symbolic tags at runtime.
• Button held down. Some touch panels generate a continuous "pressed" event while a finger is on the screen. The edge-detected Memory Discrete described above prevents the reset from firing repeatedly for the duration of the press.
• Cross-window references. If the reset button is in a popup window and the script is in the main window, the Memory Discrete must be Global. WindowMaker warns about this at save time; do not ignore the warning.
• Local language characters. For non-English operator panels, keep the tag names ASCII. The display text can be localized, but the tag dictionary should not. This avoids Unicode-escape bugs in older InTouch builds that mishandle UTF-16 tag names.

Frequently Asked Questions