NX100 Teach Pendant Play Mode Switch: External PLC Control Configuration Guide

The Yaskawa Motoman NX100 controller is widely deployed in welding, material handling, and machine-tending cells where a Programmable Logic Controller (PLC) is the cell-level authority. In those cells, the cell PLC — not the operator at the teach pendant — must decide when the robot enters PLAY (automatic) mode, when the cycle starts, and when the program resets. The standard NX100 firmware routes the mode decision through the physical three-position selector on the teach pendant, and the behavior of the PLAY position in particular is one of the most common configuration questions raised by integrators.

This reference covers the NX100 mode-selection architecture, the PLAY MODE ENABLE interlock, the Management menu settings that govern pendant-versus-external authority, the available workarounds, the fieldbus assembly mapping used for PLC hand-off, and the safety considerations that must remain in force regardless of who owns the mode decision.

1. Overview: NX100 Mode Selection Architecture

The NX100 controller reads the physical position of the teach-pendant mode selector every scan and uses that reading as the authoritative state input for the safety chain that gates servo power, program execution, and tool-center-point motion. The selector has three positions:

• TEACH — slow-speed, teach-pendant-driven programming. The controller raises teach lockout, drops high-speed operation, and limits motion to the pendant jog keys. The pendant displays the message TEACH LOCK set.
• PLAY — automatic / production mode. The controller permits program execution at full rated speed. The transition into PLAY is gated by the PLAY MODE ENABLE interlock, which requires a deliberate operator action (typically the enable / deadman paddle) before motion is allowed.
• REMOTE — mode authority is released to an external device, most commonly a PLC over DeviceNet, EtherNet/IP, Profibus, or a parallel I/O rack. The pendant selector position still reflects local intent, but the firmware accepts a mode change request from the external source.

When the operator moves the selector from TEACH to PLAY, the controller does not immediately drop teach lock. Instead, the pendant displays Push PLAY MODE ENABLE. The operator must then perform a secondary action — pressing the enable switch on the pendant or, in some installations, holding the deadman paddle in the centered position — to confirm the mode transition. This two-step human action is a deliberate safety design that prevents an operator from sweeping the switch through PLAY on the way to REMOTE and accidentally energizing live motion in a populated work envelope.

The implication for any cell where the PLC is intended to own the mode decision is fundamental: the operator must still walk through PLAY on the pendant selector before the controller will accept the PLC's request. The role of the NX100 parameters and the fieldbus mapping is to ensure that, once the selector is at REMOTE, the PLC can take over completely — including cycle start, servo on, hold, abort, and reset — without further pendant interaction.

2. Mode Selector Switch Behavior by Position

The four rows above reflect a single physical switch position (PLAY) appearing in two different safety-chain states. The intermediate state is the one most often mistaken for a firmware bug, but it is the intended behavior of the play-mode-enable interlock.

3. The PLAY MODE ENABLE Function

PLAY MODE ENABLE is a software interlock in the NX100 firmware that requires a discrete operator action before the controller honors a transition into PLAY. The action can be a button press on the pendant, a held deadman paddle, or a hardwired input brought out to a panel-mounted pushbutton. The function is engineered to make mode transitions deliberate, and it remains active across the standard NX100 firmware revisions and the supported pendant variants.

The factory default is for PLAY MODE ENABLE to be required, because the NX100 is widely deployed in cells where an operator can be standing inside the work envelope at the moment the controller transitions from teach to automatic operation. Disabling the function is not exposed in the user-accessible parameter set; it requires a service-level parameter change performed by a Yaskawa field engineer.

Three behaviors are commonly misread by integrators:

1. The Push PLAY MODE ENABLE message is not an alarm or a fault. It is a normal pending state, and the controller will sit in that state indefinitely until the enable action is performed.
2. The enable action is one-shot per mode transition. Once the controller has accepted PLAY, it does not need to be re-enabled until the next transition from TEACH or REMOTE back into PLAY.
3. The enable input on the pendant is not software-replaceable through standard Management menu changes. It is read as a discrete safety input.

The same philosophy — a deliberate, two-step human action to confirm a mode transition — is shared by other teach pendants in the industry, including the 3PE (Three-Position Enabling) device used on Universal Robots collaborative systems, where moving the pendant to automatic mode is paired with deliberate confirmation before live execution begins. Universal Robots 3PE pendant best practices describe the same workflow in a different vendor's syntax. The architectural concept is the same; the wiring and parameter names differ.

4. SETUP > OPERATE CONDITION Parameters

Under the Management tree, the path SETUP > OPERATE CONDITION exposes a set of interlocks that govern whether motion or program start is permitted from the pendant versus from an external source. Each setting toggles an internal parameter flag and is persisted across power cycles. The four key items are:

None of these settings change the position of the physical mode selector. They only govern which controller — pendant or external — is allowed to act on the current mode and which pendant actions are suppressed. The selector position is always reported back to the controller as the authoritative state.

To enter Management mode and reach this menu:

1. Press the Menu key on the pendant.
2. Navigate to Management (password protected — default is vendor-set and should be changed on commissioning).
3. Select SETUP.
4. Select OPERATE CONDITION.
5. Edit the four items above as required by the application.
6. Press Enter on each change, then Save to persist.
7. Exit Management mode to apply.

5. Why the PLAY Switch Cannot Be Fully Ignored

The selector switch on the NX100 pendant is wired to discrete mode input lines on the controller's mode-sensing board. The firmware reads these inputs every scan and routes the mode value into the safety chain that gates servo power, program execution, and tool-center-point motion. The PLAY position of the selector is treated as an authoritative state input — it tells the controller that the operator has chosen PLAY mode locally, regardless of any external signaling over the fieldbus.

There is no parameter in the standard NX100 user-accessible parameter set (S1C, S2C, S3C, S4C, or Fxxx) that disconnects the physical switch from the safety chain. The closed safety argument in NX100 firmware requires the physical switch position to match the requested mode before motion is permitted. This is the same reason Yaskawa service engineers must be called to enable or change the play mode enable behavior in custom applications — the change is below the user parameter layer.

The architectural reason is straightforward: if the controller were to allow the PLC to override the physical selector, then a fieldbus fault, a PLC scan stall, or a wiring break could leave the robot in an unknown mode with motion permitted. The physical selector is the last-resort mode signal, and the firmware is engineered to defer to it.

5.1 The Two-Step Workflow Observed in the Field

Operators migrating to a PLC-controlled cell commonly report the following workflow as a usability problem:

1. Move the pendant selector from TEACH to PLAY.
2. Press the enable paddle; the controller raises the message Push PLAY MODE ENABLE and waits for confirmation.
3. Press the cycle-start button on the pendant or on the cell HMI; teach lock is dropped and the controller enters PLAY.
4. Wait for the pendant to display TEACH LOCK set again (it does not, in PLAY — this is the common confusion point).
5. Move the pendant selector from PLAY to REMOTE.
6. Press cycle start again, this time from the PLC, to begin the master program.

The operator must therefore make two distinct physical actions on the pendant (the selector sweep and the enable confirmation) before the PLC can take over. The Management menu does not collapse those actions into one — by design.

6. PLC Integration: Mode Authority Handoff Over the Fieldbus

For applications where the PLC must own the mode decision, the NX100 supports a fieldbus interface. The most common options are:

• DeviceNet (the most common historical deployment for NX100)
• EtherNet/IP (standard on later NX100 hardware revisions and on NX100 successors)
• Profibus (common in European automotive cells)
• Parallel I/O (legacy installations and small cells)

The standard assembly for mode and start control, regardless of the fieldbus layer, exposes the following I/O group:

To make the PLC the authority, the operator must still move the pendant selector to REMOTE first. Once the selector is at REMOTE, the Management menu items discussed in Section 4 allow the PLC to issue mode changes, cycle start, and servo-on commands without further pendant interaction. The PLAY MODE ENABLE interlock is satisfied by the operator's enable-paddle action during the TEACH-to-PLAY transition; it is not repeated on the PLAY-to-REMOTE transition.

6.1 DeviceNet Assembly Example (Standard Profile)

The standard Yaskawa DeviceNet profile for the NX100 places the mode-and-control signals in a 16-bit output word from the PLC and a 16-bit input word back to the PLC. A typical mapping is:

Exact bit assignments vary by NX100 firmware revision and by the installed fieldbus option card. Always cross-check the mapping against the I/O assignment table in the project documentation before commissioning. The Yaskawa Motoman controller documentation is available through the Motoman product portal and the Yaskawa corporate site; specific manuals are released per controller serial range and must be matched to the hardware in the cell.

7. Workarounds and Field-Proven Approaches

Because the PLAY position cannot be ignored at the firmware level, three practical workarounds are used in the field to make PLC-driven mode authority less operator-intensive. Each is described below with its intended application and its limitations.

7.1 Workaround 1: Dedicated Play-Enable Output from the PLC

Some integrators wire a panel-mounted Play Mode Enable pushbutton that closes a discrete input on the NX100. The PLC can drive a relay that mimics the enable button press, allowing the PLC to advance through the play mode enable prompt without operator intervention at the pendant. The pendant selector is still moved to PLAY by the operator, but the enable confirmation is automated.

This approach keeps the operator in the loop for the deliberate selector action while removing the secondary enable-paddle step. It is the most common field workaround for cells where the PLC must take over quickly once the operator finishes teaching.

7.2 Workaround 2: Hardwired Selector Switch Bypass (Service-Level)

Remove the pendant selector and route its mode lines directly from the PLC's output modules or from a dedicated mode-control relay. This requires a service call to have Yaskawa configure the mode input as externally sourced, and the change is logged in the controller's service record. The controller's safety chain still requires the physical mode signal to be present, but the source becomes the PLC rather than the pendant switch.

This is the most invasive workaround and is generally reserved for cells where the pendant is permanently removed from the work envelope (e.g., a guarded cell with no operator access during production). The cell's risk assessment must be updated to reflect the change.

7.3 Workaround 3: PLC-Supervised Two-Step Interlock

Keep the pendant selector wired normally, but add PLC logic that prevents the master program from starting until both:

• The pendant selector is in REMOTE, AND
• A PLC_Ready_To_Run flag is asserted by the cell HMI.

This makes the two-step operator action (PLAY then REMOTE then cycle start) a deliberate decision that the PLC can supervise. The operator still has to move through PLAY, but the PLC ensures that nothing starts until REMOTE is confirmed and the cell conditions are safe. This is the least invasive workaround and is appropriate for most cells.

7.4 Comparison of the Three Workarounds

8. Configuration Procedure: Enabling External Mode Authority

1. Press the Menu key on the NX100 pendant and log into Management mode (password required; vendor default should be changed on commissioning).
2. Navigate to SETUP > OPERATE CONDITION.
3. Set Prohibit pendant start to ENABLED to block pendant-driven program start.
4. Set Prohibit pendant servo on to ENABLED to block pendant-driven servo energization.
5. Set External mode switch enable to ENABLED to allow the PLC to issue mode changes.
6. Leave Play mode enable required at its current value (typically read-only in the user menu).
7. Press Enter on each change, then Save to persist.
8. Exit Management mode to apply the new configuration.
9. Move the pendant selector to REMOTE.
10. Confirm the operator presses the enable paddle if the controller prompts for it (only if the selector passed through PLAY during the sweep).
11. Issue the PLAY mode request from the PLC over the fieldbus.
12. Verify the NX100 acknowledges the mode change and clears teach lock.
13. Issue Servo On from the PLC.
14. Issue Cycle Start from the PLC to begin program execution.

9. Verification Checklist

After configuring external mode authority, verify each item below before releasing the cell to production:

• Pendant selector in REMOTE: no Push PLAY MODE ENABLE prompt appears.
• PLC mode request is echoed in the mode status register within one fieldbus scan.
• Servo-on command from the PLC is honored without pendant interaction.
• Cycle start from the PLC begins program execution.
• Pendant cycle start button is ignored (prohibited by Management setting).
• Pendant servo-on button is ignored (prohibited by Management setting).
• Error and alarm codes propagate back to the PLC alarm word.
• E-stop on the cell drops motion regardless of mode source.
• Light curtain or area scanner breach drops motion regardless of mode source.
• PLC scan stall (PLC in stop) is detected by the NX100 and raises a fieldbus alarm.
• Loss of fieldbus connection raises a fieldbus alarm and holds the robot in the current mode without re-energizing motion.

10. Sample Ladder Logic for External Play Mode Control

The following ladder snippet illustrates a typical Allen-Bradley / Rockwell Logix Designer pattern for hand-off to the NX100. The exact tag names depend on the cell PLC and the DeviceNet / EtherNet/IP assembly configuration.

// Inputs
NX100_ModeStatus_Play    : BOOL;  // Bit from NX100 input word
NX100_ModeStatus_Remote  : BOOL;  // Bit from NX100 input word
NX100_ServoOn_Status     : BOOL;  // Bit from NX100 input word
NX100_InMotion           : BOOL;  // Bit from NX100 input word
PLC_CellReady            : BOOL;  // Cell-level safety chain OK
PLC_OperatorStartPB      : BOOL;  // Operator start pushbutton on HMI
PLC_OperatorStopPB       : BOOL;  // Operator stop pushbutton on HMI

// Outputs
PLC_ToNX100_PlayModeReq  : BOOL;  // Bit to NX100 output word (mode request)
PLC_ToNX100_ServoOn      : BOOL;  // Bit to NX100 output word (servo on)
PLC_ToNX100_CycleStart   : BOOL;  // Bit to NX100 output word (cycle start)
PLC_ToNX100_CycleStop    : BOOL;  // Bit to NX100 output word (cycle stop)
PLC_ToNX100_ErrorReset   : BOOL;  // Bit to NX100 output word (error reset)

// Ladder rung 1: request PLAY mode when cell is ready and selector is at REMOTE
PLC_ToNX100_PlayModeReq := PLC_CellReady AND NX100_ModeStatus_Remote AND NOT NX100_ModeStatus_Play;

// Ladder rung 2: enable servos after PLAY mode is confirmed
PLC_ToNX100_ServoOn := NX100_ModeStatus_Play AND PLC_CellReady AND NOT PLC_ToNX100_CycleStop;

// Ladder rung 3: cycle start (one-shot on rising edge of operator pushbutton)
PLC_ToNX100_CycleStart := PLC_OperatorStartPB AND NX100_ServoOn_Status AND NOT NX100_InMotion;

// Ladder rung 4: cycle stop (level-sensitive)
PLC_ToNX100_CycleStop := PLC_OperatorStopPB OR NOT PLC_CellReady;

// Ladder rung 5: error reset (one-shot on rising edge after alarm clears)
PLC_ToNX100_ErrorReset := PLC_OperatorStartPB AND NOT NX100_InMotion AND NOT PLC_ToNX100_CycleStop;

Three points to highlight in the logic above:

1. The PLC does not issue PLAY unless the pendant selector is already at REMOTE. Attempting to issue PLAY while the selector is at TEACH or PLAY will be rejected by the NX100 safety chain.
2. Servo-on is gated by PLC_CellReady, which represents the cell E-stop, light curtain, and safety-door chain. The NX100 will hold the robot in a safe state if the cell safety chain breaks, regardless of what the PLC requests.
3. Cycle start is one-shot on the operator pushbutton's rising edge to avoid retriggering the start sequence on every scan.

11. Safety Considerations

The two-step play mode enable is a feature, not a bug. It is engineered to prevent an operator from moving the mode switch and immediately energizing motion without conscious confirmation. The following safety items must remain in force even after configuring the PLC for external authority:

• Cell E-stop circuit must remain hardwired to the safety relay, not the PLC. The PLC may supervise the E-stop state, but it must not be the only device that drops motion on E-stop activation.
• Safety fence interlock must drop motion independent of mode. A door-open event should force a controlled stop or a category-1 stop regardless of the current NX100 mode.
• Mode change to PLAY must not bypass any light curtain or area scanner. If a scanner is muted, the muting logic must be supervised by a safety PLC or safety relay, not by the standard PLC.
• Operator presence detection in the work envelope must be honored in all modes. A presence sensor that places the robot in teach speed when the operator is inside the envelope must not be disabled in PLAY mode.
• The pendant itself must remain reachable from outside the guarded space. Removing the pendant from a cell where the operator needs to access the work envelope violates the cell's risk assessment.

12. Troubleshooting Matrix

Frequently Asked Questions