Rockwell-automation Logix5000 Controllers Sequential Function Charts P Manual de usuario descargar pdf (Pagina 18)

Chapter 1 Design a sequential function chart

If you want to

Then select or set this

member

Data type Details

Determine how long a step has been active

(milliseconds)

T DINT

When a step becomes active, the Timer (T) value resets and then starts to count up in

milliseconds. The Timer continu

es to count up until the step goes inactive, regardless of

the Preset (PRE) value.

Set a flag when the step has been active for

a specific length of time (milliseconds)

PRE DINT

Enter the time in the Preset (PRE) member. When the Timer (T) reaches the Preset

value, the Done (DN) bit turns on and stays on until the step becomes active again.

As an option, select Use Expression and click Define to enter a numeric expression

that calculates the time at runtime.

DN BOOL

When the Timer (T) reaches the Preset (PRE) value, the Done (DN) bit turns on and

stays on until the step becomes active again.

Set a flag if a step did not execute long

enough

LimitLow DINT Enter the time in the Limit Low (LimitLow) member (milliseconds).

• If the step goes inactive before the Timer (T) reaches the LimitLow value, the

AlarmLow bit turns on.

• The AlarmLow bit stays on until you reset it.

• To use this alarm function, turn on (select) the Alarm Enable (AlarmEn) bit.

As an option, enter a numeric expression that calculates the time at runtime.

AlarmEn BOOL To use the alarm bits, turn on (select) the Alarm Enable (AlarmEn) bit.

AlarmLow BOOL

If the step goes inactive before the Timer (T) reaches the Limit Low value, the

AlarmLow bit turns on. The bit stays on until you reset it.

To use this alarm function, turn on (select) the Alarm Enable (AlarmEn) bit.

Set a flag if a step is executing too long LimitHigh DINT Enter the time in the Limit High member (milliseconds).

• If the Timer (T) reaches the LimitHigh value, the AlarmHigh bit turns on.

• The AlarmHigh bit stays on until you reset it.

• To use this alarm function, turn on (select) the Alarm Enable (AlarmEn) bit.

As an option, enter a numeric expression that calculates the time at runtime.

AlarmEn BOOL To use the alarm bits, turn on (select) the Alarm Enable (AlarmEn) bit.

AlarmHigh BOOL

If the Timer (T) reaches the Limit High value, the AlarmHigh bit turns on. The bit

stays on until you reset it.

To use this alarm function, turn on (select) the Alarm Enable (AlarmEn) bit.

Do something while the step is active

(including first and last scan)

X BOOL The X bit is on the entire time the step is active (executing).

Typically, we recommend that you use an action with a N Non-Stored qualifier to

accomplish this.

18 Rockwell Automation Publication 1756-PM006F-EN-P - October 2014

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