Ch 3: Timers - PLC and HMI Programming (Studio 5000)

Wade Wittmus

TON (timer on-delay), TOF (timer off-delay), RTO (retentive timer on-delay)

Name three common timer instructions

One-thousandths of a second (millisecond)

What is the time increment used with all timer instructions in the studio 5000 software

TT (timer timing) bit

Which element from the timer structure shows the incrementing time once a timer instruction starts timing?

EN (enable) bit

Which control bit of the timer structure is true whenever there is logic continuity to a timer?

DN (done) bit

Which control bit of the timer structure shows that the accumulated value is equal to the preset value?

Retentive: retain value, even if interrupted. Non-Retentive: reset to 0 if interrupted

Explain the difference between a retentive and non-retentive instruction.

nonretentive

Is the TON instruction a retentive or nonretentive instruction

needs a logically true path

Does the TON instruction require a logically true path or false path to the instruction in order to start operating?

needs to stay true to continue operating

Once a TON instruction starts timing, what must happen with the logic continuity of that run for the TON instruction to continue operating?

a base tag (base tag: internal to the process)

What tag type is a timer instruction?

a tag

What must be created for a timer instruction before a preset value may be entered?

TT and EN

Which control bits will be true when a TON is in the act of timing?

EN and DN

Which control bits will be true when a TON has completed timing but still has logic continuity to the instruction?

Non-retentive

Is the TOF instruction a retentive or nonretentive instruction?

When TOF is on (the timer instruction resets the ACC value to zero)

Under what condition does the ACC value of a TOF timer reset to zero?

DN and EN

Which control bits will be true when a TOF has logic continuity to the instruction?

TT and DN

Which control bits will be false when the TOF timer instruction is done timing?

Retentive

Is the RTO instruction a retentive or nonretentive instruction?

RES (reset)

What is needed to reset an RTO instruction?

Timer/counter tab

Where is the RES instruction located on the language element tool bar in the studio 5000 software?

EN and TT

Which control bits will be true when an RTO is in the act of timing?

EN and DN

Which control bits will be true when an RTO has completed timing, but still has logic continuity to the instruction?

Retentive capabilities

What is the main difference between the TON instruction and RTO instruction?

Same name tag

What must an RTO instruction and RES instruction have in common for the instructions to function together?

They all share the same predefined timer structure

What do RTO, TOF, and TON instructions have in common?

a unique tag associated to it

What must each timer instruction have?

Preset (PRE), accumulator (ACC), enable (EN) bit, timer timing (TT) bit, and done (DN) bit ([RES] reset for RTO instructions)

What elements make up the structure of a timer?

Preset (PRE) element

Numerical value that can be programmed in milliseconds to define the total amount of time that the timer instruction will run (stored as a DINT)

Accumulator (ACC) element

Displays the incrementing time in milliseconds starting at zero

the ACC and PRE elements are equal

When does the timer instructions stop running?

Control when the timer instruction is active, running, or stopped (control bits are boolean values; 1 or 0; true or false)

What do control bits do?

Enable (EN) bit

____ bit is triggered on when there’s logic continuity applied; triggered off when rung logic continuity is not present

Timer timing (TT) bit

____ bit is triggered on when the timer instruction is initiated and the ACC is running. Stays on until values of ACC and PRE elements are equal.

Done (DN) bit

____ bit is triggered on when the values of the ACC and PRE elements are equal AND the timer instruction stops running

Retentive and non-retentive

Timer instructions can be what?

Retentive

what instruction maintains its value even if logic continuity to the instruction is interrupted

Nonretentive

What instruction will reset to zero if logic continuity is interrupted?

Timer on-delay (TON) instruction (actuated for a specific amount of time/change of state)

What timer instruction will only operate if there’s logic continuity to the instruction

Base tag (an internal tag, and a timer is internal to the processor)

What tag does the timer/counter variables need?

A tag

PRE and ACC parameters are not available until what is created?

Is how many milliseconds the timer must increment (has been enabled)

The PRE of the TON timer:

The timer is timing (ACC is incrementing towards the PRE time)

TT bit is on when

The ACC equals PRE and the TON instruction is enabled

DN bit will stay on as long as:

It resets to zero

What happens when the TON instruction loses continuity?

Goes from ON to OFF

When does the TOF instruction operate?

when the logic continuity turns off

When does the TOF instruction start timing?

True

T/F: does the TOF instruction have the same structure as the TON instruction?

Equals PRE

When a TOF timer is off, the ACC:

ACC value is 0 and the timer resets

a TOF timer is ON, the ACC:

Turns on at the beginning

Does the DN bit turn on at the beginning or end of a timing TOF instruction?

Logic continuity is lost

When does the TOF timer start timing?

TT and DN bits

What bit(s) turn off when the TOF instruction is done timing?

True

T/F: RTO Instruction will start timing when the logic continuity turns true

False

T/F: RTO instruction does not retain the ACC value when the instruction is false

RES (reset) instruction

What do you need to reset an RTO instruction?

False: RTO, TOF, and TON instructions have the same structure

T/F: an RTO instruction has a different structure than the TOF and TON instructions

TON instruction (DN, EN, and TT bit operate the same)

what instruction (and bit functions) is similar to the RTO instruction?

EN turns off; DN stays on (ACC value is retained even if off)

After it is done timing and the switch turns OFF for an RTO instruction: the EN bit turns (ON/OFF) and DN bit turns (ON/OFF)

False: you can reset an RTO instruction if continuity is lost AND the reset switch that connects to the RES instruction is on

T/F: An RTO instruction has to be done to be able to reset the instruction

True

T/F: Anytime there’s a logical path to a RES instruction, the RTO instruction with the same tag will reset whether or not that RTO instruction is done