Priority Override

The PriorityOverride block supports driving the outputs based on the priority of the connected application components. There can be different control program logic components driving the outputs at different priority levels. This block decides the priority level at which the output must be driven. This block supports up to 16 priority levels that can be connected to different application components.

The Priority1 value has the highest priority and Priority 16 the lowest priority. The block provides an output called PriorityOut. The value of the highest priority is set as the output PriorityOut. The PriorityOut slot of the PriorityOverride block can be linked only to a modulating/binary output.

The block can be used in both LON and BACnet applications. This block provides the PriorityArray mechanism in case of BACnet objects. This block details do not get downloaded to the controller in case of BACnet. In case of LON, the PriorityArray mechanism is internally achieved using Override blocks. The information of the override blocks get downloaded to the LON controller. Hence there would be a difference in function block count between BACnet and LON application when this block is used.

During upload the PriorityOverride block is depicted as part of the ControlProgram, depending on the number of application components driving the outputs. If there is only one application components driving the output, the ControlProgram wiresheet would show a direct link from that application component to the output. If there are more than one application component driving the output, the PriorityOverride block would be depicted in the logic with outputs being driven at different priority levels.

Analog Inputs

Range
Input Name Low High Input Value Description
priority1 through priority16 >=- infinity <+ infinity Unconnected or invalid Output = highest priority input (priority1 is top priority and priority16 is lowest priority). If no inputs are valid, then the output is also invalid.
priority16 >=- infinity <+ infinity Unconnected or invalid Output = highest priority input (priority1 is top priority and priority16 is lowest priority). If no inputs are valid, then the output is also invalid.
defaultValue >=- infinity <+ infinity unconnected defaultValue = invalid
invalid defaultValue = invalid

Outputs

Range
Output Name Low High Description
PriorityOut >=- infinity <+ infinity PriotityOut = highest priority input.

Example

Set the Inputs to the following:

  1. Priority 1  = Unconnected
  2. Priority 2  = Invalid
  3. Priority 3  = 50
  4. Priority 4  = 60
  5. Priority 5  = -20
  6. Priority 6  = 80
  7. Priority 7 = 30
  8. Priority 8 =Unconnected
  9. Priority 9 =Unconnected
  10. Priority 10 =Unconnected
  11. Priority 11 =Unconnected
  12. Priority 12 =Unconnected
  13. Priority 13 =Unconnected
  14. Priority 14 =Invalid
  15. Priority 15 =40
  16. Priority 16 =10

The output is set as Invalid. Priority 2 is invalid. The highest priority value is set as the output.

The properties of the Priority Override function block are listed in the table below.

S.No. Desciption LON BACnet
1 The input to the priority slot of the Priority Override function block can be a physical point,software point, or function blocks but cannot be a constant. Applicable Applicable
2 The PriorityOut slot can be connected to only one physical point which can be modulating output or binary output. Applicable Applicable
3 The memory incrementation depends on the type of input block. Applicable Applicable
4 The FB count in the Resource Usage View is only incremented when the Priority Override block contains a Valid Link and a Valid Knob. Applicable Not Applicable
5 If there are valid links from priority levels 1 to 8, FB count is incremented by 1. Applicable Not Applicable
6 If there are valid links from priority levels 9 to 15, FB count is incremented by 2. Applicable Not Applicable
7 If there are valid links greater than priority level 15, FB count is incremented by 3. Applicable Not Applicable
8 The FB count in the Resource Usage View is not incremented at all. Not Applicable Applicable