Updating software or firmware of a machine or plant is a complex task and different devices have different requirements to the update or installation of software. To support this, the SoftwareUpdateTypeprovides several options where a vendor can select the parts that are necessary for the software update.

All these options are exposed as optional Referencesof the SoftwareUpdateType. A Servercan choose which options it wants to support (the Profiles section describes valid combinations of options).

This way the Server can choose between Direct-Loading, Cached-Loadingor FileSystem based Loadingand it may use additional optional features like manual power cycle, parameter backup / restore or confirmation.

A Software Update Clientneeds to check which options are exposed by the Serverand how the Serverbehaves during the update (a Software Update Clientis described in 8.3.5).

There are situations where it is preferable to prepare the device explicitly before the installation and resume operation explicitly after the installation. The PrepareForUpdateStateMachine, which is described in 8.4.8can be used for this task.

This can be the case, when several devices of a machine should be updated at once. All devices have to be prepared first to ensure that all are waiting for an update. After that they can be updated by the Client. At the end after all individual updates are complete the devices can resume operation.

Or a device requires the behavior to enter a safe state (e.g., reaching a safe area) to be able to update the software.

If the installation comprises several steps (e.g., backup parameters, install firmware, restore parameters). The steps can be encapsulated by the Prepareand Resume Methodsto ensure consistency between all the steps.

The Direct-Loadingoption provides a model where the installation is part of the transfer. To support the Direct-Loadingmodel the Serverhas to provide the Current Version. This includes parameters like the version number, a release date or patch identifiers. With this information the Clientcan decide if an update is required and which version to install.

The Software Packageis transferred using the TemporaryFileTransferType(OPC 10000-5). This includes the installation itself so that the installation option is not used.

For Direct-Loadingthe DirectLoadingTypeis used, which is described in 8.4.4.

The Cached-Loadingoption provides a model where the transfer of the Software Packageand its installation are separate steps. To support the Cached-Loading model the Server has to providethe Current Versionand the Pending Version. Optionally the Fallback Versioncan be supported.

With the Current Versionthe Clientcan decice if an update is required and which version to transfer. With the Pending Versionthe Clientcan ensure to install the desired version. With the Fallback Versionthe Clientcan install an alternative version.

Software Packagesare transferred using the TemporaryFileTransferType (OPC 10000-5). The new software may be transferred in the background without stopping the device. The actual installation of the software can be done later using the installation option.

For Cached-Loadingthe CachedLoadingTypeis used, which is described in 8.4.5.

The Cached-Loading option with a self-contained Software Packageand concrete definition of the version information can be too restrictive for some devices. E.g., if new software should be installed. For this use case the FileSystem based Loadingprovides an open structure of files and directories where a Clientcan read and write. These files could be e.g., configuration, setup files or recipes. Note: The FileSystemexposed in the address space may not be congruent with the actual file system of the device.

The purpose of the directories and files is not part of this specification. It needs to be known by the Clientand the Server. Other companion specifications could add this definition for specific types of devices. If accessed by a Software Update Client,the FileSystemroot can be used to store and install the files.

For FileSystem based Loadingthe FileSystemLoadingTypeis used, which is described in 8.4.6.

Using the Cached-Loadingoption or the FileSystemoption, a transferred Software Packageor file needs to be installed explicitly (compared to the implicit installation of Direct-Loading). Therefore, the InstallationStateMachineTypeshall be used (see 8.4.9). It can either be used to install a Software Package(Cached-Loading) or a list of files from the FileSystem (File System based Loading).

The update Clientsare often operated by human users. Since an update normally is a long process, the user would like to see the current state. At a first glance the percentage can give a hint about completion of the update, especially if several devices are updated at the same time. But if there are unexpected delays or errors the user needs a detailed textual description about the current update action or issue.

This can be accomplished with the UpdateStatus Variable (see 8.4.1.8). A Clientcan subscribe to it for a user display. At least if a state machine is in an error state the UpdateStatusshould provide a meaningful error message for the user.

If the device cannot keep the parameters during the update, it shall support the Parameters Objectof the SoftwareVersionType (see 8.4.1.7). If supported by the Server, theupdate Clientshould perform a backup of the parameters before and restore the parameters after the software update.

The confirmation option supports the use case of 8.2.1.9: A Clientmay set a ConfirmationTimeoutbefore the installation. After every reboot of the Server caused by the update, it shall wait this time for a call to the Confirm Method.If the call is not received the Servershall perform a rollback to enable a working Client – Serverconnection again. This state machine is defined in 8.4.11.

The power cycle option is intended for devices where a manual power cycle is required. During the installation the state WaitingForPowerCycleinforms the user that it is time to turn the power off and on again. The PowerCycleStateMachineTypeis defined in 8.4.10.

If an instance of the SoftwareUpdateTypesupports the power cycle option, the UpdateBehavior RequiresPowerCycle shall indicate if this might happen for an installation.

This power cycle state machine is used in combination with the installation. For Cached-Loadingit may be used in the Installingstate of the InstallationStateMachineType. For Direct-Loadingit may be used during the transfer of the new software with the TemporaryFileTransferType (OPC 10000-5) of the DirectLoadingType.