General Description

Enable Input

Many function blocks have an Enable input. "Enabled" means that FB is executed. "Disabled" means that FB or some features are disabled. If the input is not connected, its value is null, which means "Enabled". The underlined value is the default value.

 

Output Function blocks with Interlock Input and Virtual Position Output

The interlock input, when set to 1, will enable the output of the block and when set to 0, the output of the block will be closed (0%) or Off (0%).

Example: The electrical reheat is only switched on when the fan is running.

 

If a logic is required which checks whether an output is open or running (valve or fan open or running), the virtual output should always be used for this, since the output model and all times are represented here. Then also a BACnet override or a valve exercising are covered.

 

Null value

The "null" value can be set and checked like any other value in the Logic. All unconnected inputs are initialized with the "null" value.

Non-connected inputs and outputs

An unconnected Input has always the value "null". An output has no default value, the value is calculated depending on the inputs. Parameter always have a default value which is underlined in the pictures. The default can also be a "null" value.

Periodic and Event program folders

There is a "Periodic program" folder with 500ms cycle time and an "Event program" folder. Typically, hardware inputs are connected to the Event program folder. The event program folder is periodically executed every 1000ms or immediately if an input changes. Points can be exchanged between the folders.

BACnet and physical Output principle

Physical outputs added to the controller do not automatically create associated BACnet points. An output is first written to a BACnet function block. Via BACnet, the value can be overwritten or set to Out-Of-Service. The output of the BACnet function block is connected to the physical output.

Failure handling

All FBs where an error can occur (i.e. when dividing by 0) log the error together with the Execution Order of the corresponding FB. The FB "Error" displays the last error that occurred on the current Wiresheet. At the end of the programming there should be no error. The "Error" FB should be the last function block on every Wiresheet.

Mix of different data types

For easy programming, all data types can be connected to the inputs and outputs. False is considered as 0 and True as 1.

Negate the inputs and outputs

For some FBs, the inputs and outputs in the function block can be negated to improve legibility and avoid additional negator FBs.

Datatypes

Since enumerations in BACnet start with the number 1, it is advisable that all enums also start with 1.

Input, Output and Parameter slots

The output slots are located at the top of the FB and the inputs at the bottom. This brings the arrangement of the FBs on the wire sheet up and corresponds to the "naming conventions of AX developments". The parameters only become visible by opening the "Property Sheet". Outputs require a relatively large amount of memory, namely 6 bytes of RAM.

Input has higher Priority than Parameter

There are parameters marked with (In & Par). In addition to this parameter, there is a corresponding input slot that has the same name, but without "Par" at the end, since the names must be unique. If the input is not connected or the input has the value "null", then the parameter is used. The input slot therefore has priority over the parameter. Only the input slot is described in detail in the documentation, while the parameter shows the default value.

About honIrmControl Palette

If honIrmControl palette is not visible on the left pane, you can click Window > Side Bars > Palette to add the honIrmControl palette.

 

Figure 1:honIrmControl Palette

As shown in the above figure, honIrmControl palette contains the following items:

Any of these objects except PhysicalPoints can be dragged onto the wire sheet of Periodic program or Event program. PhysicalPoints need to be dragged and dropped onto the On board IO folder. Make the connections between physical points, BacnetObjects, and function blocks to create a Control Program or an Application.

General Description for Platforming

Backward compatibility to Spyder Function Blocks:

Many function blocks are Spyder Classic compatible. Often the slot names have been adapted to Niagara kitControl. Often additional inputs, outputs or parameters are included. Sometimes the function is only reached with another function block.