Conditional Sequencer
medium
Advances each step only when that step's own completion input is on.
What it teaches
Builds on Single-Trigger Sequencer by giving each state its own transition condition. Start enters Step 1, then separate Done inputs advance Steps 1, 2, and 3. Inputs for other states are ignored, providing the foundation for sequences driven by sensors, timers, permissives, and operator confirmations.
Parameters
| Tag | Direction | Type | Default | Description |
|---|---|---|---|---|
| In_Start | Input | BOOL | 0 | Starts Step 1 from Idle |
| In_Step1Done | Input | BOOL | 0 | Advances Step 1 to Step 2 |
| In_Step2Done | Input | BOOL | 0 | Advances Step 2 to Step 3 |
| In_Step3Done | Input | BOOL | 0 | Completes Step 3 and returns to Idle |
| In_Reset | Input | BOOL | 0 | Returns the sequencer to Idle |
| Sts_Step1Active | Output | BOOL | 0 | 1 only while Step 1 is active |
| Sts_Step2Active | Output | BOOL | 0 | 1 only while Step 2 is active |
| Sts_Step3Active | Output | BOOL | 0 | 1 only while Step 3 is active |
| Sts_Step | Output | DINT | 0 | 0=Idle, 1=Step1, 2=Step2, 3=Step3 |
Required behavior
- A fresh block starts in Idle with Sts_Step at 0 and all active-step flags off.
- In_Start advances Idle to Step1. In_Step1Done advances Step1 to Step2, In_Step2Done advances Step2 to Step3, and In_Step3Done returns Step3 to Idle.
- Only the transition input assigned to the current step can advance the sequence; inputs assigned to other steps are ignored.
- At most one transition occurs per scan, even when several transition inputs are on together.
- Exactly one active-step flag is on in Steps 1-3. All active-step flags are off in Idle.
- In_Reset wins over every transition input and returns the sequencer to Idle.