Topic: DMD0180

TMRDOWN - Down Timer

The Down Timer (TMRDOWN) has a single ladder logic input leg which both enables and resets the Timer. If the input logic is ON, the Down Timer will begin timing down from the Preset value. When the input logic is OFF, the Timer is reset and the Timer's accumulator value is set to the Preset value.

 

The yellow triangle in the upper left corner indicates the Down Timer is a Multi-Scan instruction.

 

Parameters:

Note: Use the F9 key (Element Browser) or Down-Arrow key (Auto-Complete) at any time to see a complete list of the memory locations that are valid in the current field of the instruction.

 

Timer Struct - specifies a unique Timer structure that will be used by this instruction.

 

Preset - is the amount of time after which you want some action to take place. The Down Timer has a resolution of 1 millisecond. The maximum value for a Timer Preset is 2,147,483,647 milliseconds. The Preset value can be specified in one of two ways:

 

Constant - specified using the Time format (HH : MM : SS : mmm).

The maximum Time value in this form is 569 hours, 31 minutes, 23 seconds, and 647 milliseconds. If needed, the value entered for the Timer Preset will be normalized to its standard value. For example, if you entered a value of  97 Seconds, that value will be converted and displayed as 1 Minute and 37 Seconds.

When editing the Constant Preset value, the following keystrokes are available to make entering the value easier and faster:

    • h - takes you to the Hours field

    • m - takes you to the Minutes field

    • s - takes you to the Seconds field

    • mm - takes you to the Milliseconds field

 

Variable - designates a location that contains the total number of milliseconds desired for the Preset. This can be any readable numeric location.

 

Status Display:

The yellow triangle in the upper left corner indicates this is a Multi-Scan instruction.

 

The Down Timer instruction has a single ladder logic input leg labeled (E/R), which both enables and resets the Timer.

 

The Down Timer instruction provides several status values that can be used elsewhere in your ladder program. Their values are updated each time the TMRDOWN instruction is processed. The syntax for using them is <timer struct>.<flag name>, for example, T7.Acc.

 

  • .Acc (Accumulator) - a 32-bit signed value that represents the time remaining to reach 0
     
  • .Done - is ON any time the Down Timer is enabled and it's accumulator value (.Acc) is 0
     
  • .Reset - is ON if the input logic is OFF, or if the Down Timer is being reset by an RSTT instruction
     

  • .Zero - is ON any time the Down Timer's accumulator value (.Acc) is 0
     

  • .Timing - is ON if the Down Timer is enabled and the accumulator value (.Acc) is not 0
 

See Also:

 

Rung Example: