Topic: DMD0430
COMMON_TIMER - Common Timer Editor
When a new Timer is added to the ladder logic the Common Timer Editor will be used. This editor contains all of the possible types of Timers with timing diagrams for each type to help choose the Timer that is most appropriate for the type of timing that needs to be done. When editing an existing Timer, that Timer type's specific editor will be used.
Parameters:
Note: Use the F9 key or click the 'three dot box' at the right edge of the parameter field to open the Default Element Selection Tool (the Element Picker or the Element Browser) or use the Down-Arrow key (Auto-Complete) on any parameter field to see a complete list of the memory locations that are valid for that parameter of the instruction.
The selections in the Choose a Timer Instruction group choose the specific type of Timer to add. Choose from the following:
- TMR - Up Timer
- TMRA - Accumulating Up Timer
- ONDTMR - On Delay Timer
- OFFDTMR - On Delay Timer
- TMRDOWN - Down Timer
- TMRADOWN - Accumulating Down Timer
- TMRAG - Global Accumulating Up Timer
Timer Struct specifies which Timer number to edit, and by extension, the name of the Timer's associated structure. This can be any of the System-created Timers, or any user-created Timer. The default Memory Configuration contains 255 predefined Timers named T0 through T255.
Preset is the amount of time after which you want some action to take place. All Timers have a resolution of 1 millisecond. The maximum value for a Preset is 2,147,483,647 milliseconds. The Preset value can be specified in one of two ways:
Constant means the Preset is a fixed amount of time and can only be changed by editing the instruction. The Preset value is specified using the Time format (HH : MM : SS : mmm). The maximum Time value in this form is 596 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, m, s, and mm move the edit cursor to the Hours, Minutes, Seconds or milliseconds fields respectively.
Variable allows the Preset to be changed while the PLC is running. The Preset is specified as a numeric memory location that will contain the total number of milliseconds desired (from 0 to 2,147,483,647). This can be any readable numeric location.
The Input Leg Diagram will changes as the Timer Type is changed. It will show the different arrangements of ladder logic input legs for the different Timers. Pay particular attention to whether the Timer has a single input leg or two input legs:
On Timers with a single input leg labeled (E/R), it will function as both the Enable and the Reset. This means if the input leg logic is ON the Timer is enabled and will begin to accumulate time. If the input leg logic is OFF the Timer is disabled and reset meaning the accumulator value will return to 0 and the Timer's associated structure fields will be reset.
On Timers with two input legs, the first input leg (EN) enables and disables the Timer. When this input logic is ON, the Timer will begin accumulating time. When this input logic is OFF, the Timer will stop timing, but the accumulator and the status flags will retain their current values. If this input logic comes back ON, the Timer will continue to accumulate time. The second input leg (RST) is the Timer Reset. When this input logic is ON the Timer will be reset meaning the accumulator value will return to 0 and the Timer's associated structure fields will be reset. The Reset leg has priority over the Enable leg, that is if both input legs are ON, the Timer will reset.
The Timing diagram will change as the Timer Type is changed. It will show how the selected Timer and it's associated structure members operate while the Timer is running.
The Show AB-style Timer Structure Bits checkbox will toggle between timing diagrams showing only the structure bits with Do-more labels, and timing diagrams with only the structure bits that match those of Timers in Allen Bradley PLCs. Enabling this selection allows users that are familiar with timers in Allen Bradley PLCs to see structure members they recognize.
Checking Do not show this again will disable the use of the Common Timer Editor in this project. This option can be enabled again in the View -> Options -> Ladder tab -> Editing section by selecting either Use only with new Timers (the default) or Use with new and existing Timers.
Termination Scan Behavior:
All Timers - with one exception - have termination logic. This means if the Timer instruction is contained within a Program, a Task, or a Stage, the Timer will automatically be reset any time that Program, Task, or Stage stops executing because of an End Program, End Task, or Disable Stage respectively.
The Global Accumulating Up Timer (TMRAG) instruction does NOT have termination logic, meaning that it will retain it's accumulated time and the state of it's internal flags even if it is contained within a Program, a Task, or a Stage, that is disabled.
Refer to the Help topic on Termination Behavior for detailed information on the programming elements that have termination logic.
Timer Structure Members:
All Timers have an associated structure with fields that can be used in the ladder program. The structure fields are updated whenever the Timer instruction is processed in the PLC scan. The syntax for using them is <Timer structure>.<field name>, for example, T7.Acc.
.Acc (read/write) is a 32-bit signed value that represents the total accumulated time whenever the Timer is enabled. If the Timer is still enabled after the Preset is reached, the .Acc value keeps incrementing to a maximum of 2,147,483,647 ms (596 hrs, 31 min, 23.647s), it does not wrap.
.Done (read-only) will be ON any time the Timer's accumulator value (.Acc) is greater than or equal to the Timer's Preset value.
.Zero (read-only) will be ON any time the Timer's accumulator value (.Acc) is 0.
.Timing (read-only) will be ON if the Timer is enabled, and is NOT being held in Reset by the Reset Input leg or a Reset Timer (RSTT) instruction. Will remain ON after .Done turns ON.
.Reset (read-only) will be ON if the reset (RST) leg's input logic is TRUE, or if the Timer is being reset by a Reset Timer (RSTT) instruction.
.TT (read-only) will be ON if the Timer is enabled, and is NOT being held in Reset by the Reset Input leg or a Reset Timer (RSTT) instruction. Will turn OFF when .DN turns ON.
.EN (read-only) will be ON any time the Timer's input logic is TRUE, and the Timer is NOT being held in Reset by the Reset Input leg or a Reset Timer (RSTT) instruction.
.DN (read-only) will be ON any time the Timer's input logic is ON and it's accumulator value (.Acc) is greater than or equal to the Timer's Preset value.
See Also:
TMRADOWN - Accumulating Down Timer
TMRAG - Global Accumulating Up Timer
Related Topics: