TOFR — Off-Delay Timer

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

Operands

Name	Type
`timer`	`FBD_TIMER`

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

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

.DN holds 1 while TimerEnable is 1, and remains 1 for the preset duration after TimerEnable drops to 0.

ExhaustTimer.TimerEnable := MachineRunning;
ExhaustTimer.PRE := 30000;
TOFR(ExhaustTimer);

ExhaustFan := ExhaustTimer.DN;

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.