Programming - First steps
P.
42 of 349
Process image: Respond to
changes only
Separate Power On and Off
A telegram for ON and a separate
telegram for OFF
The Enertex
®
EibPC copies the activities on the bus in its cache (from the process image). Typically,
every ms the program is passed through again. The Enertex
®
EibPC examines at which point the
cache has been changed and processes the corresponding lines once again. This means in the
above example, if the switch once sends an ON at 1/0/0 (previously this was OFF), the lamp is
switched ON. In the next program flow (after 1 ms) the cache of 1/0/0 is already ON and thus, as
expected, an ON is not sent once again.
Suppose we have an installation as in Figure 7.
If the closing-switch “ON“ is pressed, the lamp should turn on and the dimmer is to go to 80%.
When the switch is OFF, the lights will go out.
EibPC
EibPC
RS 232
ON-switch
'1/0/0'
Lamp - binary
'1/1/1'
Dimmer – Percent
'1/1/2'
KNX Bus
OFF-Switch
'1/0/1'
Figure 7: Block diagram of Power On and Off
If activated, our ON switch will send only ON at 1/0/0. The OFF-switch will send only OFF on 1/0/1.
Because of the properties of the process image, the Enertex
®
EibPC responds to changes only. If we
forget this, it might seem as if the following program was not running correctly - but this is not the
case - and we will explain immediately why.
HandbuchEibPC_USA-30.odt, 2017-05-11
Enertex
®
Bayern GmbH - Erlachstraße 13 - 91301 Forchheim - [email protected]