# CL171 Drum Instruction: Time Base

Instructions · `CL171 Drum Instruction: Time Base` · verification: source checked

The Drum instruction simulates an electromechanical drum sequencer. It sequences through 1 to 16 steps and turns ON up to 16 physical outputs or internal control relays in a user-defined pattern. With Time Base selected, each step advances automatically after its specified Duration elapses, and a Completion Flag turns ON when the sequence completes.

## Specification

| Property | Value |
|---|---|
| Language | ladder |
| Code | Drum |
| Group | Drum |

### Parameters

| Name | Description | Data type |
|---|---|---|
| Base | The Drum instruction operates on Time Base, Event Base, or Time & Event Base. For Time Base, choose the time increment: milliseconds, seconds, minutes, hours, or days. |  |
| Current Step | Memory address where the Current Step number is stored. | DS memory address |
| Elapsed time in step | Memory address where the Elapsed Time in Step is stored. | TD memory address |
| Completion flag | Control Relay assigned as the Completion Flag. | Control Relay (C bit) |
| Enable Jog Input | Selecting Enable Jog Input turns on an additional rung that allows the user to jump to the next Step each time the Jog input transitions from OFF to ON. |  |
| Load New Step Number | Selecting Load New Step turns on an additional Step No Input rung that allows the user to jump to a specified Step. The new Step Number is held in a DS-type memory address. The Step No Input is edge triggered. |  |
| Number of Steps | Determines the number of steps in the sequence. | 1 to 16 |
| Number of Outputs | Determines the number of outputs available during the sequence. | 1 to 16 |
| Outputs | Outputs assigned for the sequence; they can be physical outputs and/or internal control relays. The number of Outputs should match Number of Outputs. |  |
| Duration | Time Duration assigned for each Step. The number of Steps should match Number of Steps. | time duration |
| Output Pattern | Grid where each cell corresponds to a combination of one Step number and one Output number. | grid |

## Safety

- Number of Steps is limited to 1 to 16.
- Number of Outputs is limited to 1 to 16.

## Study notes

- Time Base advances each step automatically after the specified Duration has elapsed.
- Time increments available for Time Base are milliseconds, seconds, minutes, hours, or days.
- Current Step must be stored in a DS-type memory address; Elapsed Time in Step must be stored in a TD-type memory address.
- Enable Jog Input adds a rung; an OFF-to-ON transition on the Jog input jumps to the next Step.
- Load New Step Number adds a Step No Input rung; an OFF-to-ON transition copies the DS-type new Step Number to Current Step.
- Outputs can be physical outputs and/or internal control relays; the number of configured Outputs should match Number of Outputs.
- The Output Pattern grid has one cell for each combination of Step number and Output number.
- The Output Address Fill Down button enters consecutive output addresses automatically; the Fill Down button helps enter time Durations quickly.
- Example: Step durations are 10 s, 20 s, 30 s, and 40 s; C1 turns ON at completion; X002 resets the Drum instruction; X003 jumps to the step number loaded in DS2; X004 jumps to the next step.

## Sources

1. [Drum Instruction: Time Base](https://cdn.automationdirect.com/static/helpfiles/click/Content/171.htm) (accessed 2026-10-26)

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