Connections

For drivers that need a network address, two connections cannot use the same address (except OPC DA and MQTT), so the same PLC cannot be reached with S7 and OPC UA at the same time. For every connection an internal Bool tag, named after the connection like PLC_Proses_Baglanti, is added automatically. Live writes its value (1 = connected); it can be used in animations, alarms and scripts.

The data type list of a tag narrows to the types the driver of its connection supports, and the address is validated against the rules of the driver. All drivers work over Ethernet. There is no serial line driver; for devices on a serial network use an Ethernet gateway or an OPC server.

These rules apply to all PLC drivers.

• Each connection runs in its own thread; a device that does not respond does not delay the other connections.
• A read cycle of at least 100 ms is applied for PLC and simulator tags. Only changed values are passed on, at most every 100 ms per connection.
• Writes are made between reads and the written tag is read back. A write is rejected while the connection is down.
• If the connection cannot be made or drops, the driver retries after 1 s, 2 s and 5 s, then every 10 s.
• A tag that cannot be read is removed from the read set and retried every 30 s; the other tags are not affected.

Studio never connects to a device. Online › Test connections… shows for each connection whether a TCP connection can be opened (it waits at most 2 s). No protocol test is made: the S7 session, the PUT/GET permission, the OPC UA security selection, the user name and the password are tried only in Live. The Diagnostics tab of the Inspector lists the target and the number of bound tags of each connection.

The states appear in the Connections section of the Live system menu and in the PLC connection status control placed on a screen. The Event view shows the connection established, lost, could not be established and unstable entries.

Even when the connection is up, a single tag may be unreadable, for example with a wrong address or a data block that does not exist. Only that tag gets bad quality and the connection stays Connected. An object bound to a bad-quality tag is drawn faded gray. The message the driver produces for a tag error is not shown in Live; to find the cause, verify the address in Studio and check the error table on the driver page.

For OPC UA, MQTT and OPC DA connections the user name stays in the project and the password does not. The password is not written to the project file; sharing, backing up or uploading the project to Live does not carry it. You enter the password in Live:

• The Settings authorization is required to enter a password.
• In the Connections section of the system menu, click the Enter password button next to the connection that asks for one.
• Type the password and press Save. Communication restarts and the connections drop and reconnect briefly.

The password you enter is stored unencrypted in the baglanti_sifreleri.json file in the data folder of the project on the Live computer. Open the folder only to the account that runs Live, using Windows permissions.

• A connection has a single address; there is no automatic switch to a backup PLC.
• Enabled is set only in the design. There is no button or function to switch a connection on and off while Live is running.
• After changing a connection setting, save the project and upload it to Live; Live establishes the connections when the project is opened.
• The station name, computer name and operating mode in the Device configuration section are only information stored in the project. Live does not read them.