06 programming timer and counter instructions Training PLC Allen Bradley

TON OPERATIONThe TON instruction starts accumulating time when the rung goes true, and continues until one of the following happen: • The rung goes false • The accumulated value equals i

DAY 2

SESSION 2

LADDER LOGIC PROGRAMMING – TIMER &

COUNTER

Be able to

• Describe the function of an on-delay timer

• Describe the function of an off-delay time

• Describe the instances in which one would use a retentive

timer

• Describe the function of an up-counter

• Describe the function of a down-counter

• Describe the instances in which one would use an up- versus a down-counter

• Define preset value, accumulative value, and timer or counter

address

SUB-WINDOW : TIMER / COUNTER

Timer is used to delay turning on or off output for maximum 9.1

hours

Counter is used to count up and down over a range of -32,768 to

+32,768

TIMER INSTRUCTIONS

• Timer Off Delay (TOF)

• Retentive Timer On (RTO)

TIMER ON DELAY (TON)

Use TON instruction to turn an output on after the timer has been

on for a preset time interval

Status bit:

EN DN

TON Timer On Delay

TON OPERATION

The TON instruction starts accumulating time when the rung goes true, and continues until one of the following happen:

• The rung goes false

• The accumulated value equals its preset value

• A reset instruction resets the timer

• The processor resets the accumulated value when the rung condition go

false, regardless of whether the timer timed out or not

TON TIMING DIAGRAM

TON STATUS BITS

This Bit: Is Set When: Indicates: And Remains Set Until One of the

Following Occurs:

Timer Enabled

.EN (bit 15)

the rung goes true that timer is enabled • the rung goes false

• a reset instruction reset the timer

Timer Timing Bit

.TT (bit 14)

the rung goes true that a timing

operation is in progress

• the rung goes false

• the DN bit is set (.ACC = PRE)

• a reset instruction reset the timer Timer Done Bit

.DN (bit 13)

the accumulated value is equal to the preset value

that a timing operation is complete

• the rung goes false

• a reset instruction resets the timer

When the input condition is true, the processor increments the accumulated value

of Timer_1 in 1 milisecond increment

Sets the output while the timer is timing

Sets the output when the timer is done timing

TIMER ON LADDER DIAGRAM

EXAMPLE

TIMER OFF DELAY (TOF)

Use TOF instruction to turn an output off after the timer has been

off for a preset time interval

Status bit:

TOF OPERATION

The TOF instruction starts accumulating time when the rung goes

false, and continues until one of the following happen:

• The rung goes true

• The accumulated value equals its preset value

• A reset instruction resets the timer

• The processor resets the accumulated value when the rung condition go

true, regardless of whether the timer timed out or not

TOF TIMING DIAGRAM

TOF STATUS BITS

This Bit: Is Set When: Indicates: And Remains Set Until One of

the Following Occurs:

Timer Enabled

.EN (bit 15)

the rung goes true that timer is

enabled

• the rung goes false

• a reset instruction reset the timer

Timer Timing Bit

• the rung goes true

• the DN bit is set (.ACC = PRE)

• a reset instruction reset the timer

Timer Done Bit

.DN (bit 13)

the rung goes true that a timing

operation is complete

• the accumulated value is equal

to the preset value

EXAMPLE TOF

LADDER DIAGRAM

When the input condition goes false, the processor starts incrementing the accumulated value of Timer_1 in

6-milisecond increments until the input goes true

Sets the output while the timer is timing

Resets the output when the timer is done timing

RETENTIVE TIMER ON (RTO)

Use RTO instruction to turn an output on after the timer has been

on for a preset time interval

Status bit:

RTO OPERATION

The RTO instruction begins timing when its rung goes true

As long as the rung remains true, the timer updates the

accumulated value each program scan, until it reaches the preset

value

The RTO instruction retains its accumulated value even if one of

the following occurs:

• The rung goes false

• The processor faults or loses power

When the input is true, the processor starts incrementing the accumulated value of T4:2 in 6-second increments The timer values remain when the input goes false.

Sets the output when the input is true and the timer is timing

Sets the output when the input is true and the accumulated value is greater then or equal to the preset value

EXAMPLE RTO

LADDER DIAGRAM

RTO TIMING DIAGRAM

RTO STATUS BITS

This Bit: Is Set When: Indicates: And Remains Set Until One of

the Following Occurs:

Timer Enabled

.EN (bit 15)

the rung goes true that a timing

operation is in progress

• the rung goes false

• a reset instruction reset the timer

Timer Timing Bit

.TT (bit 14)

the rung goes true that a timing

operation is in progress

• the rung goes false

• the DN bit is set

• the accumulated value is equal to the preset value (.ACC = PRE)

• a reset instruction reset the timer Timer Done Bit

.DN (bit 13)

the accumulated value

is equal to the preset value

that a timing operation is complete

• the DN bit is reset with the RES instruction

EXAMPLE RTO

LADDER DIAGRAM

When the input is true, the processor starts incrementing the accumulated value of Timer_1 in 6-milisecond increments The timer values remain when the input goes false.

Sets the output when the input is true and the timer is timing

Sets the output when the input is true and the accumulated value is greater then or equal to the preset value

Resets accumulated value of Timer_1

COUNTER INSTRUCTIONS

COUNT UP (CTU)

Use CTU to increment the accumulated value by one count

Status bit:

CTU OPERATION

• When the accumulated value equals or exceeds the preset

value, the CTU instruction sets a done bit DN

• The accumulated value of a counter is retentive

• The count is retained until reset by a reset instruction (RES)

that has the same address as the counter

CTU TIMING DIAGRAM

EXAMPLE CTU

LADDER DIAGRAM

Each time the input goes from false to true, the processor increments the counter by 1

Sets the output while the counter is counting

Tells when the count is reached (ACC > or = PRE)

Reset the counter

COUNT DOWN (CTD)

Use CTD to decrement the accumulated value by one count

Status bit:

CTD OPERATION

• The done bit DN is set as long as the accumulated value is

greater than or equal to the preset value

• When the accumulated value is less than the preset value, the

done bit DN is reset

• The accumulated value of a counter is retentive

• When the accumulated value equals or exceeds the preset

value, the CTU instruction sets a done bit DN

• The accumulated value of a counter is retentive

• The count is retained until reset by a reset instruction (RES)

that has the same address as the counter

CTD TIMING DIAGRAM

EXAMPLE CTD

LADDER DIAGRAM

Each time the input goes false to true, the processor decrements the counter by 1

Sets the output while the counter is counting

Tells when the count is reached (ACC > or = PRE)

Reset the counter

TIMER AND COUNTER RESET (RES)

The RES instruction is an output instruction that resets a timer or

counter

The RES instruction executes when its rung is true

Each time the input goes false to true, the processor decrements the counter by 1

Sets the output while the counter is counting

Tells when the count is reached (ACC > or = PRE)

Reset the counter

Delay turning on an output TON

Delay turning off an output TOF

DAY 2

SESSION 3

LADDER LOGIC PROGRAMMING – CONTROL

INSTRUCTIONS