Overview KNX Gate Switch

With this function block, the assignment of one KNX variable to another can be controlled, i.e. telegrams can be passed through/blocked. Only when the enable is 1 are the telegrams at the input passed to the output. This can be used, for example, for a simple partition wall control.

Important: This function block is intended only for KNX bus addresses at the output. It is not possible to link further function blocks to the output.

What the function block is intended for
The function block is telegram-oriented: it forwards the telegrams that arrive at the input while the enable is active. It does not store any state and does not synchronise the input and the output.

Typical applications are therefore the temporary blocking of an operating point or of a connection: partition wall control, night or holiday blocking of a push button, enabling an operating point only when someone is present.

Not suitable as a selector switch: The function block is not intended for switching between several sources. When the enable is switched over, the output is not updated to the current value of the newly selected source. As long as no telegrams arrive, the output keeps the last value sent, even if the input has changed in the meantime. The parameter "Set output on FG" only mitigates this when the enable changes from 0 to 1; it does not track the value continuously. If several gate switches work on the same output address, there is no priority: the value of the last telegram sent applies.

For a true source selection, use a function block that actively transfers the value when switching over, for example the "KNX assignment 1-N value" with its trigger input.

Behaviour at control startup
At startup the function block does not send a telegram to the output address on its own. The output keeps the value that was last present on this address. This means that nothing switches unintentionally after a restart of the controller.

The value at the input is only regarded as known once a telegram has been received there. Until then the function block would send the value 0, which is why nothing is sent at all before the first telegram. If the input is connected to another function block, the value is known immediately.

If the input value is to be known already at startup, activate "Read at control startup" in the properties of the input address. The response of the actuator is adopted as the input value, but it is not forwarded to the output.

The parameter "Set output on FG" reacts to the change of the enable from 0 to 1. At startup there is no such change: if the enable is already 1, nothing is sent. If the enable changes to 1 later, before any telegram has ever been received at the input, nothing is sent either. In this case the value follows automatically with the first telegram that arrives at the input.


Inputs

E1
 Variable
 A variable must be linked to the input.
FG
 Enable
 Only when 1 is present at this input are the telegrams forwarded to the output.

Outputs
A1
 Variable
 A variable must be linked to the output.

Parameters
Set output on FG.
 With this parameter, on enable 1 a telegram with the value from the input is sent, otherwise only upon receipt of the first telegram.

This requires that a value has already been received at the input. If this is not yet the case, nothing is sent on enable so that no 0 goes onto the bus. The value then follows with the first telegram that arrives at the input.
Update cyclically
 For this function block, this common parameter is only effective while the enable is 1. The first cyclic telegram is sent only after the set time has elapsed, and only if a value has already been received at the input. This prevents a telegram with the value 0 from being sent at startup.
Update outputs on startup
 This common parameter is not available for this function block. It would update the output at startup regardless of the enable and thereby send a telegram with the value 0 as long as no telegram has been received yet.




See also common parameters of all function blocks.