Remark 1: Enable login

If Enable login is set to Yes, all received telegrams are checked with regard to the CODESYS login service.

Note

It is recommended to activate the automatic login detection only for those projects for which this function is absolutely required because it slows down communication via the serial interface and also influences the PLC performance.

If the connection is directly made via RS-232, a login telegram will only be detected if the same parameters as used by CODESYS (Baudrate=19200 Baud, Stop bits=1, Parity=None, Data bits=8 Bit) are set when initializing the interface.

The same applies if the connection is made via RS-232/RS-485 interface converters. The login telegram can only be detected if the initialization parameters have the same values as the parameters set in CODESYS. Because for such an application usually more than one devices are connected to the RS-485 transmission line the following has to be observed additionally:

The CODESYS login telegram does not contain a device address. Thus, the service is first identified by all devices connected to the RS-485 transmission line that can be programmed using CODESYS and the interface of which is able to read the login telegram (interface with parameter Enable login set to Yes). Due to this, telegram collisions can occur during the subsequent acknowledgement of the login request by these devices, resulting in an interruption of the communication.

If the connection between CODESYS and the PLC is established via modem, the communication is not influenced by the interface parameters set in the PLC configuration. The parameter values required for the modem used have to be set. Once the initialization is completed, the mode processes the received telegrams according to the parameter settings. Also the assignment between login request and an individual PLC is guaranteed because the connection is established using the modem’s phone number or MSN.

The login with CODESYS first causes a reinitialization of the interface. All blocks accessing this interface are locked during the online session, i.e. they do not perform any function. During this period the block outputs have the following values:

DONE = FALSE

ERR = TRUE

ERNO = PROTOCOL_PROTECTED = 16#301F = 12319

The blocks will be reactivated after the logout by CODESYS.

The login monitoring for an interface is only done if CODESYS is not already logged in via another interface (Ethernet, ARCNET or other COM).