An Ignition Edge 8 gateway can transfer Allen-Bradley PLC tag values into PAC Control variables with a Gateway event script that calls system.tag.writeAsync. The critical licensing constraint is that a workflow tested successfully in trial mode can stop after activation when the paid license does not include the Compute module required to run the script.
Identify the licensing failure
The reported transfer used a valueChanged Gateway event to initiate writes. It worked during the Ignition Edge 8 trial but stopped immediately after the standard paid license was activated. Adding the Compute module restored operation, isolating the failure to licensed script execution rather than the Allen-Bradley connection, PAC Control destination, or write method.
| Configuration | Observed result | Engineering conclusion |
|---|---|---|
| Ignition Edge 8 trial | Data transfer operated | The trial enabled the required Gateway scripting feature. |
| Activated license without Compute | Transfer stopped | The deployed license did not authorize the event-script workflow. |
| Activated license with Compute | Transfer operated | Compute enabled the required Gateway script execution. |
Use the supported Ignition 8 write path
In this architecture, the Gateway script reads or receives the changing Allen-Bradley tag value and writes it toward the PAC Control variable with the existing Ignition function:
system.tag.writeAsyncThe evidence does not provide the tag paths, function arguments, provider names, or data types. Preserve the paths and conversion logic already proven in trial mode; do not replace them while diagnosing a license-dependent failure. Ignition 8 changed its tag implementation from version 7, so instructions written for version 7 cannot be assumed to provide an equivalent event mechanism.
Restore and verify the transfer
- Confirm that the transfer works under the Ignition Edge 8 trial configuration and record the source tag, destination variable, event trigger, and script used.
- Activate the intended production license and reproduce the failure without changing the script or tag mappings.
- Check whether the license includes the Compute module required for the
valueChangedGateway script workflow. - If Compute is absent, obtain the module through the appropriate Ignition licensing channel and apply the updated license.
- Change the Allen-Bradley source value and verify that the corresponding PAC Control variable updates after the event script executes.
The reported Compute addition cost $400 for that purchase, but this is not evidence of a current or universal list price. Confirm current pricing and license contents before procurement.
Deployment decision
Treat trial validation and production-license validation as separate acceptance tests. Before purchasing or activating the production license, verify that every required Gateway event and scripting capability is included. If a transfer works in trial mode but fails only after activation, inspect licensed module availability before modifying communications, tag paths, or PAC Control logic.
FAQ
Why did my Ignition Edge 8 tag transfer stop after licensing?
The trial enabled a Gateway valueChanged script that the activated base license did not include. In the reported configuration, adding the Compute module restored the transfer.
Does Ignition Edge 8 need Compute to run valueChanged Gateway scripts?
Yes for the documented Ignition Edge 8 workflow: the Compute module was required to execute the Gateway event script that copied the Allen-Bradley value to PAC Control.
How do I write an Allen-Bradley tag value to PAC Control in Ignition 8?
Trigger a Gateway script from the source value change and perform the destination write with system.tag.writeAsync. Verify that the production license includes Compute, then change the source value and confirm the PAC Control variable updates.