RTOR — Retentive Timer

Structured Text retentive timer function block. Uses FBD_TIMER; the ST equivalent of ladder RTO.

Operands

Name	Type
timer	FBD_TIMER

FBD_TIMER Tag Members

Member	Type	Meaning
.EnableIn	BOOL	1 lets the instruction run; 0 holds all outputs unchanged. Normally 1.
.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

RTOR is the Structured Text function-block equivalent of the ladder RTO instruction. It operates on an FBD_TIMER tag.

Like TONR, but .ACC retains its value when TimerEnable drops to 0. Timing resumes where it left off. Clear the accumulator by setting .Reset to 1.

Example

RunHours.TimerEnable := MachineRunning;
RunHours.Reset := ResetMaint;
RunHours.PRE := 28800000;
RTOR(RunHours);

MaintAlert := RunHours.DN;

Common Mistakes

• Setting .EnableIn := 0 to pause the timer. EnableIn = 0 freezes all outputs — .ACC, .EN, .TT, .DN — without advancing them. To stop timing, drop .TimerEnable to 0 instead and leave .EnableIn at 1.

Related

• RTO — the ladder-logic equivalent
• TONR, TOFR — other ST timer function blocks