Drums are a great tool when you’ve got a simple sequence of events that need to occur at set time intervals or as a result of predefined events.
Time Sequenced Drums turn bits on or off for set amounts of time. ¬†Below is one such drum. ¬†
Time that bits are held for is listed on the left side of the chart. ¬†
Bits that are turned on or off are listed on the top of the chart (A, B, C, D, E & F). ¬†
The sequence starts on from the top (the 9 second interval) and works it’s way down.
If this Drum were turned and left on it would operate for 54 seconds (9+15+5+7+6+12).
Lets look at what happens during those 54 seconds. ¬†The * indicates that all values not mentioned are held at the value they had in the previous time interval:
Seconds ¬† ¬†0 – ¬†9 ¬†A is turned on, everything else is turned off.
Seconds ¬† 9 – 24 ¬†B is turned on. *
Seconds 24 – 29 A & B are turned off, C & D are turned on. *
Seconds 29 – 36 C is turned off, E is turned on. *
Seconds 36 – 42 E is turned off, F is turned on. *
Seconds 42 – 54 D is turned off. *
Event Sequenced Drums differ from Time Sequenced Drums in 1 area. ¬†Instead of holding states for a period of time, they hold states until an event occurs. ¬†An event is when a specified bit transitions from low to high.
Some drums have a Continuous Mode option that causes the Drum to start over after it has reached the end of it’s sequence.