KNX Telegram Output

This function block is the interface from the program to the KNX bus. At a defined moment it sends a telegram to the group address linked at the output. The moment is determined by the trigger, the value that is sent by the type. For example, on a rising edge at the input a telegram with the value 1 can be sent, on a falling edge nothing.

Besides the two fixed values for on and off, the value of the input can also be passed on unchanged. This allows analogue values such as setpoints, brightness levels or temperatures to be written to a group address.

What the block is not intended for:

Not to pass changes inside the program on to other function blocks. A direct connection between the blocks is sufficient for that. If no group address but only another function block is linked at the output, no telegram is created.

Not as a replacement for a selector switch or for switching between several values. The block has only one input and one value to send.

Not to block or release a flow of telegrams, the KNX telegram gate is intended for that.

Not to check whether an actuator has accepted the command. The feedback monitoring is intended for that, it sends the command again automatically if the feedback fails to appear.

Behaviour during start-up of the controller: The block always waits until the start delay of the page has elapsed. The start delay is a property of the page and applies to all blocks on it, it is set in the properties of the page. The sequence is:

During the start delay: The controller generally does not send any telegrams. In this time the input often changes several times because the blocks build up their initial values. The block evaluates the triggers but only remembers that a telegram has to be sent. Any number of changes therefore results in a single pending send.
Start delay elapsed: If "At start" is set to Do not send, the block continues in normal operation from this moment on and the pending send is dropped. Deliberately no additional waiting takes place, so that no trigger is lost during the first seconds.
With Send on difference and Always send the read requests for the input and the output address are sent now. This would not have been possible earlier, because nothing goes onto the bus during the start delay.
Waiting time at start: The configured waiting time then runs, during which the answers to the read requests can arrive.
After the waiting time: The start behaviour is carried out once and the block changes over to normal operation.

If no start delay is set for the page, the sequence begins directly with step 2. The waiting time at start is then the only period during which the read answers can arrive.

Important: At start a telegram is only sent if a value is actually present at the input. With an internal connection to another block this is the case immediately. If a KNX address is linked at the input, the value is only considered known once a telegram or the answer to a read request has been received. Otherwise a 0 would be sent that was never calculated.

The common option "Update at start" is not offered for this block, the start behaviour is set exclusively with the parameter "At start". The common option "Update cyclically" does take effect, but it also sends only after start-up and only if the input value is known.

Inputs
TR	Trigger	Trigger input. Together with the parameter trigger it determines the moment of sending and with the types "On/Off" and "Input value" it also supplies the value.
Outputs
A1	Variable	A variable must be linked to the output so that telegrams can be sent. Connections to other function blocks are possible, but then no telegrams are sent. The data type of the telegram results from the linked variable.
Parameters
	Trigger	Determines when a telegram is sent. On change: Sends the telegram on every change of value at the input. 0->1 Rising edge: Sends the telegram on change at the input from 0 to a value other than 0. 1->0 Falling edge: Sends the telegram on change at the input from a value other than 0 to 0. On every telegram: Sends even if a telegram on the input address carries the same value as before. This only makes sense if a KNX address is linked at the input, with an internal connection this setting behaves like "On change".
	Type	Determines which value is sent. On/Off: With the input other than 0 the "Value output on" is sent, otherwise the "Value output off". On only: The "Value output on" is always sent, regardless of the state of the input. Off only: The "Value output off" is always sent. Input value: The value of the input is sent unchanged. This is how analogue values are written. The two values for on and off are not used in this case.
	At start	Determines what happens after the controller has started up. In all settings the following applies: without a value at the input nothing is sent. Do not send: Nothing is sent after the start, the first telegram is created with the next trigger. Send on difference: The block compares the value it would send with the current value of the group address linked at the output. A telegram is only sent if the two differ. This is the usual setting: the bus is updated after the start without creating unnecessary telegrams. Always send: After the start a telegram is sent once, even if nothing has changed and the bus already carries the correct value. After an update, existing projects keep the setting "Do not send" so that the familiar behaviour does not change. Newly created blocks start with "Send on difference".
	Value output on	Value for the output in the on state. Used with the types "On/Off" and "On only".
	Value output off	Value for the output in the off state. Used with the types "On/Off" and "Off only".
	Waiting time at start in s	Time in seconds that is waited in addition to the start delay of the page before the start behaviour is carried out. During this time the answers to the read requests can arrive. The default of 10 seconds is sufficient for most installations. Only effective if a telegram is sent at start.
	Read addresses at start	After the start delay one read request each is sent for the input and the output address. This way the block knows the actual state on the bus and can carry out the comparison at start. Only effective if a telegram is sent at start.
	Minimum send interval in s	Smallest interval between two telegrams in seconds, switched off with the value 0. If a send request occurs during the blocking time, the value is not lost: after the time has elapsed the value valid at that moment is sent once. This protects the bus against floods of telegrams when the input changes very quickly.
	Send on value change only	A telegram is only sent if the value has changed compared with the telegram sent last. Suppresses identical repeat telegrams. Switched off by default, because with the types "On only" and "Off only" repeated sending of the same value is usually intended.

See also common parameters of all function blocks.

KNX Telegram Output

Inputs

Outputs

Parameters