TONR — On-Delay Timer

Structured Text on-delay timer function block. Uses FBD_TIMER; the ST equivalent of ladder TON.

Operands

Name	Type
timer	FBD_TIMER

FBD_TIMER Tag Members

Member	Type	Meaning
.EnableIn	BOOL	Forced to 1 each scan by the instruction call — setting it 0 has no effect
.TimerEnable	BOOL	1 runs the timer and advances ACC; 0 stops timing
.PRE	DINT	Preset target time in milliseconds
.Reset	BOOL	1 clears EN, TT, DN and sets ACC to 0
.EnableOut	BOOL	1 while the instruction is executing normally
.ACC	DINT	Accumulated time in milliseconds
.EN	BOOL	1 while TimerEnable is 1 and Reset is 0
.TT	BOOL	1 while the timer is actively counting toward PRE
.DN	BOOL	Done status — each timer (TONR, TOFR, RTOR) decides when this turns on
.Status	DINT	Packed status word — combines InstructFault and PresetInv bits
.InstructFault	BOOL	1 when the instruction hit an execution error
.PresetInv	BOOL	1 when PRE is outside its valid range

How It Works

TONR is the Structured Text function-block equivalent of the ladder TON instruction. It operates on an FBD_TIMER tag and exposes the same on-delay behaviour via named members.

When called with a true TimerEnable, the timer accumulates toward .PRE. .DN becomes 1 when .ACC reaches .PRE.

Example

MyTimer.TimerEnable := Start_Button;
MyTimer.PRE := 5000;
TONR(MyTimer);

IF MyTimer.DN THEN
    Alarm := 1;
END_IF;

Practice

Try TONR in the Long Press exercise — fire only when a button is held for two seconds.

Common Mistakes

• Trying to pause with .EnableIn := 0. The instruction call forces .EnableIn back to 1 every scan, so the assignment has no effect. To stop timing, drop .TimerEnable to 0 — that resets .ACC to 0.
• Assigning .ACC from logic to reset it (MyTimer.ACC := 0). Structured Text recomputes .ACC every scan, so a runtime write is ignored (the initial .ACC default is still honored). Clear it with .Reset := 1. The same write does take effect on the ladder TON — so don't rely on it either way; it isn't portable.

Related

• TON — the ladder-logic equivalent
• TOFR, RTOR — other ST timer function blocks