PLC ALMA Function
Execution Ladder Diagram
| Condition/State | Action Taken |
| Prescan | Rung-condition-out is cleared to false.
All of the ALMA structure parameters are cleared All alarm conditions are acknowledged. All operator requests are cleared All timestamps are cleared All delivery flags are cleared. |
| Rung-condition-in is false | Rung-condition-out is cleared to false. |
| Rung-condition-in is true | Rung-condition-out is set to true The instruction executes |
| Postscan | Rung-condition-out is cleared to false |
Function Block
| Condition/State | Action Taken |
| Prescan | Tag.EnableOut is cleared to false.
All of the ALMA structure parameters are cleared All alarm conditions are acknowledged. All operator requests are cleared All timestamps are cleared All delivery flags are cleared. |
| Tag.EnableIn is false | Tag.EnableOut is cleared to false |
| Tag.EnableIn is true | The instruction executes Tag.EnableOut is set to true |
| Instruction first run | N/A |
| Instruction first scan | N/A |
| Postscan | Tag.EnableOut is cleared to false |
Structured Text
In Structured Text, EnableIn is always true during normal scan. Therefore, if the instruction is in the control path activated by the logic it will execute.
| Condition/State | Action Taken |
| Prescan | See Prescan in the Ladder Diagram table. |
| Normal Execution | See Rung-condition-in is true in the Ladder Diagram table. |
| Postscan | See Postscan in the Ladder Diagram table. |
Examples Ladder Diagram
Function Block
An example of an ALftA instruction in Function Block is shown below. In this example, the Tank 32 Level Transmitter (Tank32LT) is monitored for alarm conditions. The Tank32LevelAck tag can be used to acknowledge all conditions of this alarm.
Structured Text
In this example, the Tank 32 Level Transmitter (Tank32LT) is monitored for alarm conditions. The Tank32LevelAck tag can be used to acknowledge all conditions of this alarm.
ALMA(Tank32Level,Tank32LT,Tank32LevelAck,0, 0);
