DL105 Micro PLC. User Manual (2003)

6-3

Drum Instruction Programming

Drum Chart

For editing purposes, the electronic drum is presented in chart form in

Representation

DirectSOFT32 and in this manual. Imagine slicing the surface of a hollow drum

cylinder between two rows of pegs, then pressing it flat. Now you can view the drum

as a chart as shown below. Each row represents a step, numbered 1 through 16.

Each column represents an output, numbered 0 through 15 (to match word bit

numbering). The solid circles in the chart represent pegs (On state) in the

mechanical drum, and the open circles are empty peg sites (Off state).

OUTPUTS

STEP

15 14 13 12 11

10 9

f F f F f f F f f f F f f F f f

f F f F F f F f f f f F f f F f

f F F F F f F F f f f f f f f f

F F f F F f F f F f f f f f f F

f f f F f f F f F f F f F f f F

f f f F f f F f F f F f F F f F

F f f F f f F F F F f F F F f F

F f F f f F f F F f f f F f f F

f f f f f f f F F f f f F f f f

f f f f f f f F F F f f f f f f

F f f f F f f f f F f f f f F f

f F f f F F f f F f F F f F F f

f f F f f f f f f f f F F f F f

f f f f f f f F f f f F F f F F

F f f f f F f F f F f F f f F F

f f F f f f f F f F f F F f f F

The mechanical drum sequencer derives its name from sequences of control

Output Sequences

changes on its electrical outputs. The following figure shows the sequence of On/Off

controls generated by the drum pattern above. Compare the two, and you will find

that they are equivalent! If you can see their equivalence, you are well on your way to

understanding drum instruction operation.

Step

Output

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6-4

Drum Instruction Programming

Step Transitions

Drum Instruction

EDRUM operation in the F1-130 includes the following features:

Parameters

S Up to 16 steps

S Time-based step transitions

S Event-based step transitions

S Up to 16 discrete outputs per drum (X, Y, or C type)

The EDRUM has 16 steps, and each step has 16 outputs. Refer to the figure below.

Each output can be either an X, Y, or C coil, offering a lot of programming flexibility.

We assign Step 1 an arbitrary unique output pattern (f= Off, F= On) as shown.

When programming the EDRUM instruction, you also determine both the output

assignment and the On/Off state (pattern) at that time. All steps use the same output

assignment, but each step may have its own unique output pattern.

Timer-Only

Drums move from one step to another based on time and/or an external event

Transitions

(input). Each step has its own transition condition which you assign during the drum

instruction entry. The figure below shows how timer-only transitions work.

Step 1

Outputs: F f f f F f F f f f f F F f f f

Increment

count timer

Has counts per

step expired?

Yes

Step 2

Outputs:

f f f

F f f f f F F f F f f F F

Use next transition criteria

The drum stays in Step 1 for a specific duration (user-programmable). The timebase

of the timer is programmable, from 0.01 seconds to 99.99 seconds. This establishes

the resolution, or the duration of each “tick of the clock”. Each step uses the same

timebase, but has its own unique counts per step, which you program. When the

counts for Step 1 have expired, then the drum moves to Step 2. The outputs change

immediately to match the new pattern for Step 2.

The drum spends a specific amount of time in each step, given by the formula:

Time in step = 0.01 seconds X Timebase x Counts per step

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6-5

Drum Instruction Programming

For example, if you program a 5 second time base and 12 counts for Step 1, then the

drum will spend 60 seconds in Step 1. The maximum time for any step is given by the

formula:

Max Time per step = 0.01 seconds X 9999 X 9999

= 999,800 seconds = 277.7 hours = 11.6 days

NOTE: When first choosing the timebase resolution, a good rule of thumb is to make

it about 1/10 the duration of the shortest step in your drum. Then you will be able to

optimize the duration of that step in 10% increments. Other steps with longer

durations allow optimizing by even smaller increments (percentage-wise). Also,

note that the drum instruction executes once per CPU scan. Therefore, it is pointless

to specify a drum timebase that is much faster than the CPU scan time.

Timer and Event

Step transitions may also occur based on time and/or external events. The figure

Transitions

below shows how step transitions work in these cases.

Step 1

Outputs: F f f f F f F f f f f F F f f f

Is Step event

true?

Yes

Increment

count timer

Has step

counts expired?

Yes

Step 2

Outputs:

f f f

F f f f f F F f F f f F F

Use next transition criteria

When the drum enters Step 1, it sets the output pattern as shown. Then it begins

polling the external input programmed for that step. You can define event inputs as

X, Y, or C discrete point types. Suppose we select X0 for the Step 1 event input. If X0

is off, then the drum remains in Step 1. When X0 is On, the event criteria is met and

the timer increments. The timer increments as long as the event (X0) remains true.

When the counts for Step 1 have expired, then the drum moves to Step 2. The

outputs change immediately to match the new pattern for Step 2.

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6-6

Drum Instruction Programming

Event-Only

Step transitions do not require both the event and the timer criteria programmed for

Transitions

each step. You have the option of programming just one of the two, and even mixing

transition types among all the steps of the drum. For example, you might want Step 1

to transition on an event, Step 2 to transition on time only, and Step 3 to transition on

both time and an event. Furthermore, you may elect to use only part of the 16 steps,

and only part of the 16 outputs.

Step 1

Outputs: F f f f F f F f f f f F F f f f

Is Step event

true?

Yes

Step 2

Outputs:

f f f

F f f f f F F f F f f F F

Use next transition criteria

Counter

Each drum instruction uses the resources of four counters in the CPU. When

Assignments

programming the drum instruction, you select the first counter number. The drum

also uses the next three counters automatically. The counter bit associated with the

first counter turns on when the drum has completed its cycle, going off when the

drum is reset. These counter values and the counter bit precisely indicate the

progress of the drum instruction, and can be monitored by your ladder program.

Suppose we program a timer drum to have

Counter Assignments

8 steps, and we select CT10 for the

CT10

Counts in step

V1010

1528

counter number

(remember, counter

CT11

Timer Value

V1011

0200

numbering is in octal). Counter usage is

shown to the right. The right column holds

CT12

Preset Step

V1012

0001

typical values, interpreted below.

CT13

Current Step

V1013

0004

CT10 shows that we are at the 1528th count in the current step, which is step 4

(shown in CT13). If we have programmed step 4 to have 3000 counts, then the step

is just over half completed. CT11 is the count timer, shown in units of 0.01 seconds.

So, each least-significant-digit change represents 0.01 seconds. The value of 200

means that we have been in the current count (1528) for 2 seconds (0.01 x 100).

Finally, CT12 holds the preset step value which was programmed into the drum

instruction. When the drum’s Reset input is active, it presets to step 1 in this case.

The value of CT12 changes only if the ladder program writes to it, or the drum

instruction is edited and the program is restarted. Counter bit CT10 turns on when

the drum cycle is complete, and turns off when the drum is reset.

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6-7

Drum Instruction Programming

Last Step

The last step in a drum sequence may be any step number, since partial drums are

Completion

valid. Refer to the following figure. When the transition conditions of the last step are

met, the drum sets the counter bit corresponding to the counter named in the drum

instruction box (such as CT0). Then it moves to a final “drum complete” state. The

drum outputs remain in the pattern defined for the last step. Having finished a drum

cycle, the Start and Jog inputs have no effect at this point.

The drum leaves the “drum complete” state when the Reset input becomes active (or

on a program-to-run mode transition). It resets the drum complete bit (such as CT0),

and then goes directly to the appropriate step number defined as the preset step.

Last step

Outputs: F F F f f f F f f F f F F F f F

Are transition

(Timer and/or

conditions met?

Event criteria)

Yes

Set

Set Drum Complete bit

CT0 = 1

Complete

Outputs: F F F f f f F f f F f F F F f F

Reset Input

Active?

Yes

Reset

Reset Drum Complete bit

CT0 = 0

Go to Preset Step

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6-8

Drum Instruction Programming

Overview of Drum Operation

Drum Instruction

The drum instruction utilizes various inputs and outputs in addition to the drum

Block Diagram

pattern itself. Refer to the figure below.

Inputs

DRUM INSTRUCTION

Outputs

Block Diagram

Start

Realtime

Jog

Inputs

(from ladder)

Reset

Drum

Preset Step

f f

F f

f f

Step

Final Drum

f f

F f

Counts/Step

Step

Pointer

Outputs

F F

f F

F f

Control

f F

F f

Timebase

f F

F f

F F

f F

f f

F F

Programming

f F

F f

f F

Selections

Events

Counter #

Pattern

Counter Assignments

CT0

Counts in step

V1000

xxxx

CT1

Timer Value

V1001

xxxx

CT2

Preset Step

V1002

xxxx

CT3

Current Step

V1003

xxxx

The drum instruction accepts several inputs for step control, the main control of the

drum. The inputs and their functions are:

S Start - The Start input is effective only when Reset is off. When Start is

on, the drum timer runs if it is in a timed transition, and the drum looks

for the input event during event transitions. When Start is off, the drum

freezes in its current state (Reset must remain off), and the drum

outputs maintain their current on/off pattern.

S Jog - The jog input is only effective when Reset is off (Start may be

either on or off). The jog input increments the drum to the next step on

each off-to-on transition.

S Reset - The Reset input has priority over the Start input. When Reset is

on, the drum moves to its preset step. When Reset is off, then the Start

input operates normally.

S Preset Step - A step number from 1 to 16 that you define (typically is

step 1). The drum moves to this step whenever Reset is on, and

whenever the CPU first enters run mode.

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6-9

Drum Instruction Programming

S Counts/Step - The number of timer counts the drum spends in each

step. Each step has its own counts parameter. However, programming

the counts/step is optional.

S Timer Value - the current value of the counts/step timer.

S Counter # - The counter number specifies the first of four consecutive

counters which the drum uses for step control. You can monitor these to

determine the drum’s progress through its control cycle. The DL105 has

64 counters (CT0 - CT77 in octal).

S Events - Either an X, Y, C, S, T, or CT type discrete point serves as

step transition inputs. Each step has its own event. However,

programming the event is optional.

WARNING: The outputs of a drum are enabled any time the CPU is in Run Mode.

The Start Input does not have to be on, and the Reset input does not disable the

outputs. Upon entering Run Mode, drum outputs automatically turn on or off

according to the pattern of the current step of the drum. This initial step number

depends on the counter memory configuration: non-retentive versus retentive.

Powerup State of

The choice of the starting step on powerup and program-to-run mode transitions are

Drum Registers

important to consider for your application. Please refer to the following chart. If the

counter memory is configured as non-retentive, the drum is initialized the same way

on every powerup or program-to-run mode transition. However, if the counter

memory is configured to be retentive, the drum will stay in its previous state.

Counter Num-

Function

Initialization on Powerup

ber

Non-Retentive Case

Retentive Case

CT(n)

Current Step

Initialize = 0

Use Previous (no

Count

change)

CT(n + 1)

Counter Timer

Initialize = 0

Use Previous (no

Value

change)

CT(n + 2)

Preset Step

Initialize = Preset Step #

Use Previous (no

change)

CT(n + 3)

Current Step #

Initialize = Preset Step #

Use Previous (no

change)

Applications with relatively fast drum cycle times typically will need to be reset on

powerup, using the non-retentive option. Applications with relatively long drum cycle

times may need to resume at the previous point where operations stopped, using the

retentive case. The default option is the retentive case. This means that if you

initialize scratchpad V-memory, the memory will be retentive.

DL105 PLC User Manual, 2nd Edition, Rev. A

6-10

Drum Instruction Programming

Drum Control Techniques

Drum

Now we are ready to put together the

Start

Control Inputs

concepts on the previous pages and

demonstrate general control of the drum

Jog

Setup

Outputs

Info.

instruction box. The drawing to the right

Reset

shows a simplified generic drum

f f

F f

f f

instruction. Inputs from ladder logic

Steps

f f

F f

control the Start, Jog, and Reset Inputs.

F F

f F

F f

The first counter bit of the drum (CT0, for

f F

F f

f F

F f

F F

example) indicates the drum cycle is

f F

f f

F F

done.

f F

F f

f F

The timing diagram below shows an arbitrary timer drum input sequence and how

the drum responds. As the CPU enters Run mode it initializes the step number to the

preset step number (typically it is Step 1). When the Start input turns on the drum

begins running, waiting for an event and/or running the timer (depends on the setup).

After the drum enters Step 2, Reset turns On while Start is still On. Since Reset has

priority over Start, the drum goes to the preset step (Step 1). Note that the drum is

held in the preset step during Reset, and that step does not run (respond to events or

run the timer) until Reset turns off.

After the drum has entered step 3, the Start input goes off momentarily, halting the

drum’s timer until Start turns on again.

Start

Reset

Hold Resume

Drum

Reset

drum drum

Complete drum

Inputs

Start

Jog

Reset

Drum Status

Step #

Drum

Complete (CT0)

Outputs (x 16)

When the drum completes the last step (Step 16 in this example), the Drum

Complete bit (CT0) turns on, and the step number remains at 16. When the Reset

input turns on, it turns off the Drum Complete bit (CT0), and forces the drum to enter

the preset step.

NOTE: The timing diagram shows all steps using equal time durations. Step times

can vary greatly, depending on the counts/step programmed.

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6-11

Drum Instruction Programming

In the figure below, we focus on how the Jog input works on event drums. To the left

of the diagram, note that the off-to-on transitions of the Jog input increments the

step. Start may be either on or off (however, Reset must be off). Two jogs takes the

drum to step three. Next, the Start input turns on, and the drum begins running

normally. During step 6 another Jog input signal occurs. This increments the drum to

step 7, setting the timer to 0. The drum begins running immediately in step 7,

because Start is already on. The drum advances to step 8 normally.

As the drum enters step 14, the Start input turns off. Two more Jog signals moves the

drum to step 16. However, note that a third Jog signal is required to move the drum

through step 16 to “drum complete”. Finally, a Reset input signal arrives which forces

the drum into the preset step and turns off the drum complete bit.

Jog

Reset

Jog

Drum

drum drum

drum

Complete

Inputs

Start

Jog

Reset

Drum Status

6,7

Step #

Drum

Complete (CT0)

Outputs (x 16)

Self-Resetting

Applications often require drums that

Start

Drum

automatically start over once they

Setup

Outputs

complete a cycle. This is easily

Start

Info.

accomplished, using the drum complete

f f

F f

Steps

Reset

f f

bit. In the figure to the right, the drum

f f

instruction setup is for CT0, so we logically

CT0

F F

f F

F f

OR the drum complete bit (CT0) with the

f F

F f

Reset input. When the last step is done,

f F

f f

f F

F f

the drum turns on CT0 which resets itself

to the preset step, also resetting CT0.

Contact X2 still works as a manual reset.

Initializing Drum

The outputs of a drum are enabled any

time the CPU is in run mode. On

Outputs

program-to-run mode transitions, the drum goes to the preset step, and the outputs

energize according to the pattern of that step. If your application requires all outputs

to be off at powerup, make the preset step in the drum a “reset step”, with all outputs

off.

Using Complex

Each event-based transition accepts only one contact reference for the event.

Event Step

However, this does not limit events to just one contact. Just use a control relay

Transitions

contact such as C0 for the step transition event. Elsewhere in ladder logic, you may

use C0 as an output coil, making it dependent on many other “events” (contacts).

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6-12

Drum Instruction Programming

Drum Instruction

Event Drum

The Event Drum (EDRUM) features time-based and event-based step transitions. It

(EDRUM)

operates according to the general principles of drum operation covered in the

beginning of this chapter. Below is the instruction as displayed by DirectSOFT32.

Counter Number

EDRUM2

Step Preset

Timebase

Discrete Output Assignment

Start

EDRUM CT aa

Step Preset K bb

(Ffff)

Control

Jog

(Ffff)

Inputs

0.01 sec/Count

Reset

K cccc

Step # Counts Event

Kdddd

Eeeee

f f

Kdddd

Eeeee

f f

Kdddd

Eeeee

f f

Step Number

Kdddd

Eeeee

f f

Kdddd

Eeeee

f f

Kdddd

Eeeee

f f

Counts per Step

Kdddd

Eeeee

f f

Kdddd

Eeeee

f f

Event per step

Kdddd

Eeeee

f f

Kdddd

Eeeee

f f

Output Pattern

Kdddd

Eeeee

f f

f= Off, F= On

Kdddd

Eeeee

f f

Kdddd

Eeeee

f f

Kdddd

Eeeee

f f

Kdddd

Eeeee f f

f f

Kdddd

Eeeee

f f

The Event Drum features 16 steps and 16 discrete outputs. Step transitions occur on

timed and/or event basis. The jog input also advances the step on each off-to-on

transition. Time is specified in counts per step, and events are specified as discrete

contacts. Unused steps must be programmed with “counts per step” = 0, and event =

“K0000”. The discrete output points may be individually assigned.

Whenever the Start input is energized, the drum’s timer is enabled. As long as the

event is true for the current step, the timer runs during that step. When the step count

equals the counts per step, the drum transitions to the next step. This process stops

when the last step is complete, or when the Reset input is energized. The drum

enters the preset step chosen upon a CPU program-to-run mode transition, and

whenever the Reset input is energized.

Drum Parameters

Field

Data Types

Ranges

Counter Number

0 - 74

Preset Step

1 - 16

Timer base

cccc

0.01 - 99.99 seconds

Counts per step

dddd

0 - 9999

Event

eeee

X, Y, C, S, T, CT

see page 4-28

Discrete Outputs

ffff

X, Y, C

see page 4-28

DL105 PLC User Manual, 2nd Edition, Rev. A

6-13

Drum Instruction Programming

Drum instructions use four counters in the CPU. The ladder program can read the

counter values for the drum’s status. The ladder program may write a new preset

step number to CT(n+2) at any time. However, the other counters are for monitoring

purposes only.

Counter Number

Ranges of (n)

Function

Counter Bit Function

CT(n)

0 - 74

Counts in step

CTn = Drum Complete

C( n+1)

1 - 75

Timer value

CT(n+1) = (not used)

CT( n+2)

2 -76

Preset Step

CT(n+2) = (not used)

CT( n+3)

3 -77

Current Step

CT(n+1) = (not used)

The following ladder program shows the EDRUM instruction in a typical ladder

program, as shown by DirectSOFT32. Steps 1 through 11 are used, and all sixteen

output points are used. The preset step is step 1. The timebase runs at (K100 x 0.01)

= 0.1 second per count. Therefore, the duration of step 1 is (5 x 0.1) = 0.5 seconds.

Note that step 1 is time-based only (event = “K0000”). And, the output pattern for

step 1 programs all outputs off, which is a typically desirable powerup condition. In

the last rung, the Drum Complete bit (CT4) turns on output Y0 upon completion of the

last step (step 10). A drum reset also resets CT4.

DirectSOFT32

Start

EDRUM CT 4

Step Preset K 1

(C34)

(Y6)

(C14)

(Y0)

(C4)

(Y5)

(Y1)

(C7)

Jog

(Y3)

(Y7)

(C30)

(Y2)

(C2)

(Y6)

(Y4)

(C10)

0.01 sec/Count: K 100

Reset

Step # Counts Event

K0005

K0000

f f

K0020

F f

f F

F f

f f

f F

f f

F f

K0150

f f

F f

f f

F f

f F

f f

K0048

f F

f f

f F

f f

f F

F F

f F

F f

K0180

f F

f f

f F

F f

f F

K0923

F f

f F

f f

F F

f F

f f

F F

K0120

f F

f f

f F

f f

F f

f f

f F

F f

K0864

F f

f F

f f

F f

f F

F f

f F

K1200

f f

F F

F f

f f

F f

K0400

C12

f F

F f

f f

f F

F f

f F

f f

K0000

C20

F f

f f

f F

f f

f F

f f

f F

F F

K0000

Eeeee

f f

K0000

Eeeee

f f

K0000

Eeeee

f f

K0000

Eeeee

f f

K0000

Eeeee

f f

CT4

Drum Complete

OUT

DL105 PLC User Manual, 2nd Edition, Rev. A

6-14

Drum Instruction Programming

Handheld

The EDRUM instruction may be programmed using either DirectSOFT32 or a

Programer

handheld programmer. This section covers entry via the handheld programmer

Drum Mnemonics

(Refer to the DirectSOFT32 manual for drum instruction entry using that tool).

First, enter Store instructions for the

Start

Setup

Outputs

ladder rungs controlling the drum’s ladder

Jog

Info.

inputs. In the example to the right, the

Mask

f f

F f

f f

timer drum’s Start, Jog, and Reset inputs

Steps

Reset

f f

are controlled by X0, X1 and X2

f f

F f

F F

f F

F f

respectively. The required keystrokes are

f F

F f

listed beside the mnemonic.

f F

F f

F F

f F

f f

F F

These keystrokes precede the EDRUM

f F

F f

f F

instruction mnemonic. Note that the

Handheld Programmer Keystrokes

ladder rungs for Start, Jog, and Reset

Store X0

ENT

inputs are not limited to being

STR

single-contact rungs.

(Repeat for Store X1 and Store X2)

After the Store instructions, enter the EDRUM (using Counter CT0) as shown:

Handheld Programmer Keystrokes

EDRUM CNT0

SHFT

ENT

ORN

ISG

ORST

After entering the EDRUM mnemonic as above, the handheld programmer creates

an input form for all the drum parameters. The input form consists of approximately

fifty or more default mnemonic entries containing DEF (define) statements. The

default mnemonics are already “input” for you, so they appear automatically. Use the

NXT and PREV keys to move forward and backward through the form. Only the

editing of default values is required, thus eliminating many keystrokes. The entries

required for the basic timer drum are in the chart below.

Drum Parameters

Multiple

Mnemonic / Entry

Default

Valid Data

Ranges

Entries

Mnemonic

Types

Start Input

STR (plus input rung)

Jog Input

STR (plus input rung)

Reset Input

STR (plus input rung)

Drum Mnemonic

DRUM CNT aa

0 - 74

Preset Step

DEF K0000

1 - 16

Timer base

cccc

DEF K0000

2 - 9999

Output points

ffff

DEF 0000

X, Y, C *

see page

4-28

Counts per step

dddd

DEF K0000

0 - 9999

Events

dddd

DEF K0000

X, Y, C, S,

see page

T, CT

4-28

Output pattern

gggg

DEF K0000

0 - FFFF

NOTE: Default entries for output points and events are “DEF 0000”, which means

they are unassigned. If you need to go back and change an assigned output as

unused again, enter “K0000”. The entry will again show as “DEF 0000”.

DL105 PLC User Manual, 2nd Edition, Rev. A

6-15

Drum Instruction Programming

Using the DRUM entry chart (two pages before), we show the method of entry for the

basic time/event drum instruction. First, we convert the output pattern for each step

to the equivalent hex number, as shown in the following example.

Step 1

Outputs:

f f f f

F f f F f f f F F f F f

- converts to:

The following diagram shows the method for entering the previous EDRUM example

on the HHP. The default entries of the form are in parenthesis. After the drum

instruction entry (on the fourth row), the remaining keystrokes over-write the

numeric portion of each default DEF statement. NOTE: Drum editing requires

Handheld Programmer firmware version 1.7 or later.

Handheld Programmer Keystrokes

NOTE: You may use the NXT and PREV keys

Start

ENT

STR

to skip past entries for unused outputs or steps.

Jog

ENT

STR

Reset

ENT

STR

Drum Inst.

SHFT

ENT

ORN

ISG

ORST

Preset Step

( DEF K0001)

Handheld Programmer Keystrokes cont’d

Time Base

( DEF K0000 )

( DEF 0000 )

SHFT

( DEF K0000 )

( DEF 0000 )

SHFT

( DEF K0000 )

( DEF 0000 )

SHFT

( DEF K0000 )

MLS

( DEF 0000 )

SHFT

( DEF K0000 )

MLS

( DEF 0000 )

SHFT

( DEF K0000 )

MLS

( DEF 0000 )

SHFT

( DEF K0000 )

MLS

( DEF 0000 )

SHFT

( DEF K0000 )

( DEF 0000 )

SHFT

Counts/

( DEF K0000 )

Outputs

Step

( DEF 0000 )

SHFT

( DEF K0000 )

MLS

( DEF 0000 )

SHFT

( DEF K0000 )

MLS

( DEF 0000 )

SHFT

( DEF K0000 )

( DEF 0000 )

SHFT

( DEF K0000 )

( DEF 0000 )

SHFT

( DEF K0000 )

MLS

skip over

unused steps

( DEF 0000 )

SHFT

( DEF K0000 )

MLS

( DEF 0000 )

SHFT

( DEF K0000 )

( DEF 0000 )

SHFT

16( DEF K0000 )

MLS

(Continued on next page)

DL105 PLC User Manual, 2nd Edition, Rev. A

6-16

Drum Instruction Programming

Handheld Programmer Keystrokes cont’d

( DEF 0000 )

skip over unused event

( DEF K0000 )

step 1 pattern = 0000

( DEF 0000 )

SHFT

MLS

( DEF K0000 )

( DEF 0000 )

SHFT

SET

( DEF K0000 )

( DEF 0000 )

SHFT

SET

( DEF K0000 )

( DEF 0000 )

SHFT

( DEF K0000 )

( DEF 0000 )

SHFT

( DEF K0000 )

( DEF 0000 )

SHFT

SET

( DEF K0000 )

( DEF 0000 )

SHFT

SET

Output

( DEF K0000 )

Events

Pattern

( DEF 0000 )

SHFT

SET

( DEF K0000 )

SHFT

( DEF 0000 )

SHFT

MLS

( DEF K0000 )

( DEF 0000 )

SHFT

( DEF K0000 )

( DEF 0000 )

( DEF K0000 )

( DEF 0000 )

( DEF K0000 )

( DEF 0000 )

( DEF K0000 )

unused steps

( DEF 0000 )

( DEF K0000 )

( DEF 0000 )

( DEF K0000 )

STR

CNT

Last rung

SHFT

MLS

NOTE: You may use the NXT and PREV keys

to skip past entries for unused outputs or steps.

DL105 PLC User Manual, 2nd Edition, Rev. A

7-2

RLL^PLUS Stage Programming

Introduction to Stage Programming

Stage Programming provides a way to organize and program complex applications

with relative ease, when compared to purely relay ladder logic (RLL) solutions.

Stage programming does not replace or negate the use of traditional boolean ladder

programming. This is why Stage Programming is also called RLL^PLUS. You won’t

have to discard any training or experience you already have. Stage programming

simply allows you to divide and organize a RLL program into groups of ladder

instructions called stages. This allows quicker and more intuitive ladder program

development than traditional RLL alone provides.

Overcoming

Many PLC programmers in the industry

“Stage Fright”

have become comfortable using RLL for

every PLC program they write... but often

RST

remain skeptical or even fearful of learning

new techniques such as stage

programming. While RLL is great at

SET

solving boolean logic relationships, it has

disadvantages as well:

STAGE!

S Large programs can become almost

unmanageable, because of a lack of

structure.

S In RLL, latches must be tediously

OUT

created from self-latching relays.

S When a process gets stuck, it is

difficult to find the rung where the

error occurred.

S Programs become difficult to modify

later, because they do not intuitively

resemble the application problem

they are solving.

It’s easy to see that these inefficiencies consume a lot of additional time, and time is

money. Stage programming overcomes these obstacles! We believe a few

moments of studying the stage concept is one of the greatest investments in

programming speed and efficiency a PLC programmer can make!

So, we encourage you to study stage programming and add it to your “toolbox” of

programming techniques. This chapter is designed as a self-paced tutorial on stage

programming. For best results:

S Start at the beginning and do not skip over any sections.

S Study each stage programming concept by working through each

example. The examples build progressively on each other.

S Read the stage Questions and Answers at the end of the chapter for a

quick review.

DL105 PLC User Manual, 2nd Edition, Rev. A

7-3

RLL^PLUS Stage Programming

Learning to Draw State Transition Diagrams

Introduction to

Those familiar with ladder program

Process States

execution know that the CPU must scan

Ladder

Inputs

Outputs

the ladder program repeatedly, over and

Program

over. Its three basic steps are:

1. Read the inputs

PLC Scan

2. Execute the ladder program

3. Write the outputs

1) Read Execute

Write

The benefit is that a change at the inputs

2) Read

Execute

Write

can affect the outputs in just a few

3) Read

(etc

)

milliseconds.

Most manufacturing processes consist of a series of activities or conditions , each

lasting for several seconds. minutes, or even hours. We might call these “process

states”, which are either active or inactive at any particular time. A challenge for RLL

programs is that a particular input event may last for just a brief instant. We typically

create latching relays in RLL to preserve the input event in order to maintain a

process state for the required duration.

We can organize and divide ladder logic into sections called “stages”, representing

process states. But before we describe stages in detail, we will reveal the secret to

understanding stage programming: state transition diagrams.

The Need for State

Sometimes we need to forget about the scan nature of PLCs, and focus our thinking

Diagrams

toward the states of the process we need to identify. Clear thinking and concise

analysis of an application gives us the best chance at writing efficient, bug-free

programs. State diagrams are just a tool to help us draw a picture of our process!

You’ll discover that if we can get the picture right, our program will also be right!

A 2-State Process

Consider the simple process shown to the

Inputs

Outputs

right, which controls an industrial motor.

We will use a green momentary SPST

Motor

pushbutton to turn the motor on, and a red

Ladder

one to turn it off. The machine operator will

Off

Program

press the appropriate pushbutton for just a

second or so. The two states of our

process are ON and OFF.

Transition condition

The next step is to draw a state transition

State

diagram, as shown to the right. It shows

the two states OFF and ON, with two

transition lines in-between. When the

OFF

event X0 is true, we transition from OFF to

ON. When X1 is true, we transition from

ON to OFF.

Output equation: Y0 = ON

If you’re following along, you are very close to grasping the concept and the

problem-solving power of state transition diagrams. The output of our controller is

Y0, which is true any time we are in the ON state. In a boolean sense, Y0=ON state.

Next, we will implement the state diagram first as RLL, then as a stage program. This

will help you see the relationship between the two methods in problem solving.

DL105 PLC User Manual, 2nd Edition, Rev. A

7-4

RLL^PLUS Stage Programming

The state transition diagram to the right is

a picture of the solution we need to create.

The beauty of it is this: it expresses the

OFF

problem

independently

the

programming language we may use to

realize it. In other words, by drawing the

diagram we have already solved the

Output equation: Y0 = ON

control problem!

First, we’ll translate the state diagram to traditional RLL. Then we’ll show how easy it

is to translate the diagram into a stage programming solution.

RLL Equivalent

The RLL solution is shown to the right. It

Set

Reset

Latch

consists of a self-latching control relay,

C0. When the On pushbutton (X0) is

OUT

pressed, output coil C0 turns on and the

C0 contact on the second row latches

itself on. So, X0 sets the latch C0 on, and

Latch

Output

it remains on after the X0 contact opens.

The motor output Y0 also has power flow,

so the motor is now on.

OUT

When the Off pushbutton (X1) is pressed,

it opens the normally-closed X1 contact,

which resets the latch. Motor output Y0

turns off when the latch coil C0 goes off.

Stage Equivalent

The stage program solution is shown to

the right. The two inline stage boxes S0

and S1 correspond to the two states OFF

and ON. The ladder rung(s) below each

OFF State

stage box belong to each respective

stage. This means that the PLC only has

Transition

to scan those rungs when the

corresponding stage is active!

JMP

For now, let’s assume we begin in the OFF

State, so stage S0 is active. When the On

pushbutton

(X0) is pressed, a stage

ON State

transition occurs. The JMP S1 instruction

Output

executes, which simply turns off the stage

SP1

Always on

bit S0 and turns on stage bit S1. So on the

OUT

next PLC scan, the CPU will not execute

stage S0, but will execute stage S1!

Transition

In the On State (stage S1), we want the

motor to always be on. The special relay

JMP

contact SP1 is defined as always on, so Y0

turns the motor on.

When the Off pushbutton (X1) is pressed, a transition back to the Off State occurs.

The JMP S0 instruction executes, which simply turns off the stage bit S1 and turns on

stage bit S0. On the next PLC scan, the CPU will not execute stage S1, so the motor

output Y0 will turn off. The Off state (stage 0) will be ready for the next cycle.

DL105 PLC User Manual, 2nd Edition, Rev. A

7-5

RLL^PLUS Stage Programming

Let’s Compare

Right now, you may be thinking

“I don’t see the big advantage to Stage

Programming... in fact, the stage program is longer than the plain RLL program”.

Well, now is the time to exercise a bit of faith. As control problems grow in complexity,

stage programming quickly out-performs RLL in simplicity, program size, etc.

For example, consider the diagram below.

Notice how easy it is to correlate the OFF

and ON states of the state transition

OFF State

diagram below to the stage program at the

right. Now, we challenge anyone to easily

identify the same states in the RLL

JMP

program on the previous page!

ON State

SP1

OUT

OFF

JMP

Initial Stages

At powerup and Program-to-Run Mode

Powerup in OFF State

transitions, the PLC always begins with all

ISG

normal stages (SG) off. So, the stage

Initial Stage

programs shown so far have actually had

no way to get started (because rungs are

not scanned unless their stage is active).

JMP

Assume that we want to always begin in

the Off state (motor off), which is how the

RLL program works. The Initial Stage

(ISG) is defined to be active at powerup. In

SP1

the modified program to the right, we have

OUT

changed stage S0 to the ISG type. This

ensures the PLC will scan contact X0 after

powerup, because Stage S0 is active.

JMP

After powerup, an Initial Stage (ISG)

works just like any other stage!

We can change both programs so that the

Powerup in ON State

motor is ON at powerup. In the RLL below,

we must add a first scan relay SP0,

latching C0 on. In the stage example to the

right, we simply make Stage S1 an initial

stage (ISG) instead of S0.

JMP

Powerup in ON State

ISG

Initial Stage

OUT

SP1

OUT

SP0

JMP

First Scan

DL105 PLC User Manual, 2nd Edition, Rev. A

7-6

RLL^PLUS Stage Programming

We can mark our desired powerup state

Powerup

as shown to the right, which helps us

remember to use the appropriate Initial

Stages when creating a stage program. It

OFF

is permissible to have as many initial

stages as the process requires.

You may recall that a stage is just a section of ladder program which is either active or

What Stage Bits Do

inactive at a given moment. All stage bits (S0 to S77) reside in the PLC’s image

Program execution always reads ladder rungs from top to bottom, and from left to

right. The drawing below shows the effect of stage bit status. The ladder rungs below

the stage instruction continuing until the next stage instruction or the end of program

belong to stage 0. Its equivalent operation is shown on the right. When S0 is true, the

two rungs have power flow.

S If Stage bit S0 = 0, its ladder rungs are not scanned (executed).

S If stage bit S0 = 1, its ladder rungs are scanned (executed).

Actual Program Appearance

Functionally Equivalent Ladder

(includes all rungs in stage)

Stage Instruction

The inline stage boxes on the left power

Characteristics

rail divide the ladder program rungs into

stages. Some stage rules are:

S Execution - Only logic in active

stages are executed on any scan.

S Transitions - Stage transition

instructions take effect on the next

occurrence of the stages involved.

S Octal numbering - Stages are

numbered in octal, like I/O points,

etc. So “S8” is not valid.

S Total Stages - The DL105 offers up

to 256 stages (S0 to S377 in octal).

S No duplicates - Each stage number

is unique and can be used just once.

S Any order - You can skip numbers

and sequence the stage numbers in

any order.

END

S Last Stage - the last stage in the

ladder program includes all rungs

from its stage box until the end coil.

DL105 PLC User Manual, 2nd Edition, Rev. A

7-7

RLL^PLUS Stage Programming

Using the Stage Jump Instruction for State Transitions

Stage Jump, Set,

The stage JMP instruction we have used deactivates the stage in which the

and Reset

instruction occurs, while activating the stage in the JMP instruction. Refer to the

Instructions

state transition shown below. When contact X0 energizes, the state transition from

S0 to S1 occurs. The two stage examples shown below are equivalent. So, the stage

Jump instruction is equal to a Stage Reset of the current stage, plus a Stage Set

instruction for the stage to which we want to transition.

Equivalent

JMP

RST

SET

Please Read Carefully - The jump instruction is easily misunderstood. The “jump”

does not occur immediately like a GOTO or GOSUB program control instruction

when executed. Here’s how it works:

S The jump instruction resets the stage bit of the stage in which it occurs.

All rungs in the stage still finish executing during the current scan, even

if there are other rungs in the stage below the jump instruction!

S The reset will be in effect on the following scan, so the stage that

executed the jump instruction previously will be inactive and bypassed.

S The stage bit of the stage named in the Jump instruction will be set

immediately, so the stage will be executed on its next occurrence. In the

left program shown below, stage S1 executes during the same scan as

the JMP S1 occurs in S0. In the example on the right, Stage S1

executes on the next scan after the JMP S1 executes, because stage

S1 is located above stage S0.

Executes on next

scan after Jmp

JMP

OUT

Executes on same

scan as Jmp

JMP

OUT

Note: Assume we start with Stage 0 active and stage 1 inactive for both examples.

DL105 PLC User Manual, 2nd Edition, Rev. A

7-8

RLL^PLUS Stage Programming

Stage Program Example: Toggle On/Off Lamp Controller

A 4-State Process

In the process shown to the right, we use

Inputs

Outputs

an ordinary momentary pushbutton to

control a light bulb. The ladder program

Toggle

will latch the switch input, so that we will

Ladder

push and release to turn on the light, push

Program

and release again to turn it off (sometimes

called toggle function). Sure, we could just

buy a mechanical switch with the alternate

on/off action built in... However, this

Powerup

example is educational and also fun!

Next we draw the state transition diagram.

OFF

A typical first approach is to use X0 for

both transitions (like the example shown

to the right). However, this is incorrect

Output equation: Y0 = ON

(please keep reading).

Note that this example differs from the motor example, because now we have just

one pushbutton. When we press the pushbutton, both transition conditions are met.

We would just transition around the state diagram at top speed. If implemented in

stage, this solution would flash the light on or off each scan (obviously undesirable)!

The solution is to make the the push and the release of the pushbutton separate

events. Refer to the new state transition diagram below. At powerup we enter the

OFF state. When switch X0 is pressed, we enter the Press-ON state. When it is

released, we enter the ON state. Note that X0 with the bar above it denotes X0 NOT.

Powerup

Push-ON

ISG

OFF State

OFF

JMP

Push-OFF

Push-On State

Output equation: Y0 = ON

JMP

When in the ON state, another push and

release cycle similarly takes us back to the

OFF state. Now we have two unique states

ON State

(OFF and ON) used when the pushbutton is

Output

released, which is what was required to solve

SP1

the control problem.

OUT

The equivalent stage program is shown to the

right. The desired powerup state is OFF, so

JMP

we make S0 an initial stage (ISG). In the ON

state, we add special relay contact SP1,

Push-Off State

which is always on.

Note that even as our programs grow more

complex, it is still easy to correlate the state

JMP

transition diagram with the stage program!

DL105 PLC User Manual, 2nd Edition, Rev. A

7-9

RLL^PLUS Stage Programming

Four Steps to Writing a Stage Program

By now, you’ve probably noticed that we follow the same steps to solve each

example problem. The steps will probably come to you automatically if you work

through all the examples in this chapter. It’s helpful to have a checklist to guide us

through the problem solving. The following steps summarize the stage program

design procedure:

1. Write a Word Description of the application.

Describe all functions of the process in your own words. Start by listing what

happens first, then next, etc. If you find there are too many things happening at once,

try dividing the problem into more than one process. Remember, you can still have

the processes communicate with each other to coordinate their overall activity.

2. Draw the Block Diagram.

Inputs represent all the information the process needs for decisions, and outputs

connect to all devices controlled by the process.

S Make lists of inputs and outputs for the process.

S Assign I/O point numbers (X and Y) to physical inputs and outputs.

3. Draw the State Transition Diagram.

The state transition diagram describes the central function of the block diagram,

reading inputs and generating outputs.

S Identify and name the states of the process.

S Identify the event(s) required for each transition between states.

S Ensure the process has a way to re-start itself, or is cyclical.

S Choose the powerup state for your process.

S Write the output equations.

4. Write the Stage Program.

Translate the state transition diagram into a stage program.

S Make each state a stage. Remember to number stages in octal. Up to

256 total stages are available in the DL205, numbered 0 to 377 in octal.

S Put transition logic inside the stage which originates each transition (the

stage each arrow points away from).

S Use an initial stage (ISG) for any states that must be active at powerup.

S Place the outputs or actions in the appropriate stages.

You’ll notice that Steps 1 through 3 just prepare us to write the stage program in Step

4. However, the program virtually writes itself because of the preparation

beforehand. Soon you’ll be able to start with a word description of an application and

create a stage program in one easy session!

DL105 PLC User Manual, 2nd Edition, Rev. A

7-10

RLL^PLUS Stage Programming

Stage Program Example: A Garage Door Opener

Garage Door

In this next stage programming example

Opener Example

we’ll create a garage door opener

controller. Hopefully most readers are

familiar with this application, and we can

have fun besides!

The first step we must take is to describe

how the door opener works. We will start

by achieving the basic operation, waiting

to add extra features later. Stage

programs are very easy to modify.

Our garage door controller has a motor

which raises or lowers the door on

command. The garage owner pushes and

releases a momentary pushbutton once to

raise the door. After the door is up, another

push-release cycle will lower the door.

In order to identify the inputs and outputs

Up limit switch

of the system, it’s sometimes helpful to

sketch its main components, as shown in

the door side view to the right. The door

Motor

Raise

has an up limit and a down limit switch.

Lower

Each limit switch closes only when the

door has reach the end of travel in the

corresponding direction. In the middle of

travel, neither limit switch is closed.

The motor has two command inputs: raise

Door

and lower. When neither input is active,

Command

the motor is stopped.

The door command is just a simple

pushbutton. Whether wall-mounted as

Down limit switch

shown, or a radio-remote control, all door

control commands logical OR together as

one pair of switch contacts.

Draw the Block

The block diagram of the controller is

Inputs

Outputs

Diagram

shown to the right. Input X0 is from the

Toggle

pushbutton door control. Input X1

energizes when the door reaches the full

To motor:

up position. Input X2 energizes when the

Ladder

Up limit

door reaches the full down position. When

Program

Raise

the door is positioned between fully up or

down, both limit switches are open.

Down limit

The controller has two outputs to drive the

Lower

motor. Y1 is the up

(raise the door)

command, and Y2 is the down (lower the

door) command.

DL105 PLC User Manual, 2nd Edition, Rev. A

7-11

RLL^PLUS Stage Programming

Draw the State

Now we are ready to draw the state transition diagram. Like the previous light bulb

Diagram

controller example, this application also has just one switch for the command input.

Refer to the figure below.

S When the door is down (DOWN state), nothing happens until X0

energizes. Its push and release brings us to the RAISE state, where

output Y1 turns on and causes the motor to raise the door.

S We transition to the UP state when the up limit switch (X1) energizes,

and turns off the motor.

S Then nothing happens until another X0 press-release cycle occurs. That

takes us to the LOWER state, turning on output Y2 to command the

motor to lower the door. We transition back to the DOWN state when the

down limit switch (X2) energizes.

Push-UP

RAISE

ISG

Powerup

DOWN State

DOWN

JMP

Push-UP State

LOWER

Push-DOWN

JMP

Output equations: Y1 = RAISE Y2 = LOWER

RAISE State

The equivalent stage program is shown to the

right. For now, we will assume the door is

SP1

down at powerup, so the desired powerup

OUT

state is DOWN. We make S0 an initial stage

(ISG). Stage S0 remains active until the door

JMP

control pushbutton activates. Then we

transition (JMP) to Push-UP stage, S1.

UP State

A push-release cycle of the pushbutton takes

us through stage S1 to the RAISE stage, S2.

We use the always-on contact SP1 to

JMP

energize the motor’s raise command, Y1.

When the door reaches the fully-raised

Push-DOWN State

position, the up limit switch X1 activates. This

takes us to the UP Stage S3, where we wait

until another door control command occurs.

JMP

In the UP Stage S3, a push-release cycle of

the pushbutton will take us to the LOWER

Stage S5, where we activate Y2 to command

LOWER State

the motor to lower the door. This continues

SP1

until the door reaches the down limit switch,

X2. When X2 closes, we transition from Stage

OUT

S5 to the DOWN stage S0, where we began.

NOTE: The only special thing about an initial

JMP

stage (ISG) is that it is automatically active at

powerup. Afterwards, it is just like any other.

DL105 PLC User Manual, 2nd Edition, Rev. A

7-12

RLL^PLUS Stage Programming

Add Safety

Next we will add a safety light feature to

Light Feature

the door opener system. It’s best to get the

main function working first as we have

done, then adding the secondary features.

The safety light is standard on many

Safety light

commercially-available garage door

openers. It is shown to the right, mounted

on the motor housing. The light turns on

upon any door activity, remaining on for

approximately 3 minutes afterwards.

This part of the exercise will demonstrate

the use of parallel states in our state

diagram. Instead of using the JMP

instruction, we’ll use the set and reset

commands.

Modify the

To control the light bulb, we add an output

Inputs

Outputs

Block Diagram and

to our controller block diagram, shown to

Toggle

State Diagram

the right, Y3 is the light control output.

Raise

In the diagram below, we add an additional

state called

“LIGHT”. Whenever the

Ladder

Up limit

garage owner presses the door control

Program

switch and releases, the RAISE or

Lower

LOWER state is active and the LIGHT

state is simultaneously active. The line to

Down limit

the Light state is dashed, because it is not

Light

the primary path.

We can think of the Light state as a parallel process to the raise and lower state. The

paths to the Light state are not a transition (Stage JMP), but a State Set command. In

the logic of the Light stage, we will place a three-minute timer. When it expires, timer

bit T0 turns on and resets the Light stage. The path out of the Light stage goes

nowhere, indicating the Light stage just becomes inactive, and the light goes out!

Output equations:

Y1 = RAISE

Y2 = LOWER

Y3 = LIGHT

Push-UP

RAISE

DOWN

LIGHT

LOWER

Push-DOWN

DL105 PLC User Manual, 2nd Edition, Rev. A

7-13

RLL^PLUS Stage Programming

Using a Timer

The finished modified program is shown to

Inside a Stage

the right. The shaded areas indicate the

ISG

DOWN State

program additions.

In the Push-UP stage S1, we add the Set

Stage Bit S6 instruction. When contact X0

JMP

opens, we transition from S1 and go to two

new active states: S2 and S6. In the

Push-UP State

Push-DOWN state S4, we make the same

additions. So, any time someone presses

the door control pushbutton, the light turns

JMP

on.

Most new stage programmers would be

SET

concerned about where to place the Light

RAISE State

Stage in the ladder, and how to number it.

The good news is that it doesn’t matter!

SP1

S Just choose an unused stage

OUT

number, and use it for the new stage

and as the reference from other

JMP

stages.

S Placement in the program is not

UP State

critical, so we place it at the end.

You might think that each stage has to be

directly under the stage that transitions to

JMP

it. While it is good practice, it is not

required (that’s good, because our two

Push-DOWN State

locations for the Set S6 instruction make

that impossible). Stage numbers and how

they are used determines the transition

JMP

paths.

In stage S6, we turn on the safety light by

SET

energizing Y3. Special relay contact SP1

is always on. Timer T0 times at 0.1 second

LOWER State

per count. To achieve 3 minutes time

SP1

period, we calculate:

OUT

3 min. x 60 sec/min

0.1 sec/count

JMP

K=1800 counts

The timer has power flow whenever stage

LIGHT State

S6 is active. The corresponding timer bit

T0 is set when the timer expires. So three

SP1

minutes later, T0=1 and the instruction

OUT

Reset S6 causes the stage to be inactive.

While Stage S6 is active and the light is on,

TMR T0

K1800

stage transitions in the primary path

continue normally and independently of

Stage 6. That is, the door can go up, down,

RST

or whatever, but the light will be on for

precisely 3 minutes.

DL105 PLC User Manual, 2nd Edition, Rev. A

7-14

RLL^PLUS Stage Programming

Add Emergency

Some garage door openers today will

Stop Feature

detect an object under the door. This halts

further lowering of the door. Usually

implemented

with

photocell

(“electric-eye”), a door in the process of

being lowered will halt and begin raising.

We will define our safety feature to work in

this way, adding the input from the

photocell to the block diagram as shown to

the right. X3 will be on if an object is in the

path of the door.

Inputs

Outputs

Next, we make a simple addition to the

Toggle

state transition diagram, shown in shaded

Raise

areas in the figure below. Note the new

Up limit

transition path at the top of the LOWER

Ladder

state. If we are lowering the door and

Program

Lower

detect an obstruction (X3), we then jump

Down limit

to the Push-UP State. We do this instead

Light

of jumping directly to the RAISE state, to

Obstruction

give the Lower output Y2 one scan to turn

off, before the Raise output Y1 energizes.

Push-UP

RAISE

DOWN

LIGHT

X2 and

LOWER

Push-DOWN

Exclusive

It is theoretically possible that the down limit (X2) and the obstruction input (X3)

Transitions

could energize at the same moment. In that case, we would “jump” to the Push-UP

and DOWN states simultaneously, which does not make sense.

Instead, we give priority to the obstruction

by changing the transition condition to the

DOWN state to [X2 AND NOT X3]. This

LOWER State

ensures the obstruction event has the

SP1

priority. The modifications we must make

OUT

to the LOWER stage (S5) logic are shown

to the right. The first rung remains

to Push-UP

unchanged. The second and third rungs

JMP

implement the transitions we need. Note

the opposite relay contact usage for X3,

to DOWN

which ensures the stage will execute only

JMP

one of the JMP instructions.

DL105 PLC User Manual, 2nd Edition, Rev. A

7-15

RLL^PLUS Stage Programming

Stage Program Design Considerations

Stage Program

The examples so far in this chapter used one self-contained state diagram to

Organization

represent the main process. However, we can have multiple processes

implemented in stages, all in the same ladder program. New stage programmers

sometimes try to turn a stage on and off each scan, based on the false assumption

that only one stage can be on at a time. For ladder rungs that you want to execute

each scan, just put them in a stage that is always on.

The following figure shows a typical application. During operation, the primary

manufacturing activity Main Process, Powerup Initialization, E-Stop and Alarm

Monitoring, and Operator Interface are all running. At powerup, three initial stages

shown begin operation.

Main Process

XXX

= ISG

Idle

Fill

Agitate

Rinse

Spin

Powerup Initialization

E-Stop and Alarm Monitoring

Operator Interface

Powerup

Monitor

Control

Recipe

Status

In a typical application, the separate stage sequences above operate as follows:

S Powerup Initialization - This stage contains ladder rung tasks done

just once at powerup. Its last rung resets the stage, so this stage is only

active for one scan (or only as many scans that are required).

S Main Process - this stage sequence controls the heart of the process

or machine. One pass through the sequence represents one part cycle

of the machine, or one batch in the process.

S E-Stop and Alarm Monitoring - This stage is always active because it

is watching for errors that could indicate an alarm condition or require an

emergency stop. It is common for this stage to reset stages in the main

process or elsewhere, in order to initialize them after an error condition.

S Operator Interface - this is another task that must always be active

and ready to respond to an operator. It allows an operator interface to

change modes, etc. independently of the current main process step.

Although we have separate processes,

Operator Interface

there can be coordination among them.

For example, in an error condition, the

Control

Recipe

Status Stage may want to automatically

switch the operator interface to the status

mode to show error information as shown

Set

Monitor

Status

to the right. The monitor stage could set

the stage bit for Status and Reset the

E-Stop and

stages Control and Recipe.

Alarm Monitoring

DL105 PLC User Manual, 2nd Edition, Rev. A

7-16

RLL^PLUS Stage Programming

How Instructions We can think of states or stages as simply dividing up our ladder program as

depicted in the figure below. Each stage contains only the ladder rungs which are

Work Inside Stages

needed for the corresponding state of the process. The logic for transitioning out of a

stage is contained within that stage. It’s easy to choose which ladder rungs are active

at powerup by using an “initial” stage type (ISG).

Stage 0

Stage 1

Stage 2

Most all instructions work just like they do in standard RLL. You can think of a stage

just like a miniature RLL program which is either active or inactive.

Output Coils - As expected, output coils in active stages will turn on or off outputs

according to power flow into the coil. However, note the following:

S Outputs work as usual, provided each output reference (such as “Y3”) is

used in only one stage.

S An output can be referenced from more than one stage, as long as only

one of the stages is active at a time.

S If an output coil is controlled by more than one stage simultaneously, the

active stage nearest the bottom of the program determines the final

output status during each scan. Therefore, use the OROUT instruction

instead when you want multiple stages to have a logical OR control of

an output.

One-Shot or PD coils - Use care if you must use a Positive Differential coil in a

stage. Remember that the input to the coil must make a 0-1 transition. If the coil is

already energized on the first scan when the stage becomes active, the PD coil will

not work. This is because the 0-1 transition did not occur.

PD coil alternative: If there is a task which you want to do only once (on 1 scan), it can

be placed in a stage which transitions to the next stage on the same scan.

Counter - In using a counter inside a stage, the stage must be active for one scan

before the input to the counter makes a 0-1 transition. Otherwise, there is no real

transition and the counter will not count.

The ordinary Counter instruction does have a restriction inside stages: it may not be

reset from other stages using the RST instruction for the counter bit. However, the

special Stage Counter provides a solution (see next paragraph).

Stage Counter - The Stage Counter has the benefit that its count may be globally

reset from other stages by using the RST instruction. It has a count input, but no reset

input. This is the only difference from a standard counter.

Drum - Realize that the drum sequencer is its own process, and is a different

programming method than stage programming. If you need to use a drum with

stages, be sure to place the drum instruction in an ISG stage that is always active.

DL105 PLC User Manual, 2nd Edition, Rev. A

7-17

RLL^PLUS Stage Programming

Using a Stage as a You may recall the light bulb on-off

Supervisory

controller example from earlier in this

Toggle

Process

chapter. For the purpose of illustration,

Ladder

suppose we want to monitor the

Program

“productivity” of the lamp process, by

counting the number of on-off cycles

which occurs. This application will require

the addition of a simple counter, but the

key decision is in where to put the counter.

Powerup

ISG

OFF State

Supervisor

Supervisor Process

JMP

Powerup

Push-ON

Push-On State

OFF

Main Process

JMP

Push-OFF

ON State

SP1

New stage programming students will

OUT

typically try to place the counter inside one the

the stages of the process they are trying to

monitor. The problem with this approach is

JMP

that the stage is active only part of the time. In

order for the counter to count, the count input

Push-Off State

must transition from off to on at least one scan

after its stage activates. Ensuring this

requires extra logic that can be tricky.

JMP

In this case, we only need to add another

supervisory stage as shown above, to “watch”

ISG

Supervisor State

the main process. The counter inside the

supervisor stage uses the stage bit S1 of the

SGCNT CT0

main process as its count input. Stage bits

used as a contact let us monitor a process!

K5000

Note that both the Supervisor stage and the

OFF stage are initial stages. The supervisor

stage remains active indefinitely.

Stage Counter

The counter in the above example is a special Stage Counter. Note that it does not

have a reset input. The count is reset by executing a Reset instruction, naming the

counter bit (CT0 in this case). The Stage Counter has the benefit that its count may

be globally reset from other stages. The standard Counter instruction does not have

this global reset capability. You may still use a regular Counter instruction inside a

stage... however, the reset input to the counter is the only way to reset it.

DL105 PLC User Manual, 2nd Edition, Rev. A

7-18

RLL^PLUS Stage Programming

Power Flow

Our discussion of state transitions has shown how the stage JMP instruction makes

Transition

the current stage inactive and the next stage (named in the JMP) active. As an

Technique

alternative way to enter this in DirectSOFT32, you may use the power flow method

for stage transitions.

The main requirement is that the current stage be located directly above the next

(jump-to) stage in the ladder program. This arrangement is shown in the diagram

below, by stages S0 and S1, respectively.

Equivalent

All other rungs in stage...

JMP

Power flow

transition

Recall that the stage JMP instruction may occur anywhere in the current stage, and

the result is the same. However, power flow transitions (shown above) must occur as

the last rung in a stage. All other rungs in the stage will precede it. The power flow

transition method is also achievable on the handheld programmer, by simply

following the transition condition with the stage instruction for the next stage.

The power flow transition method does eliminate one stage JMP instruction, its only

advantage. However, it is not as easy to make program changes as using the stage

JMP. Therefore, we advise using stage JMP transitions for most programmers.

Stage View in

The stage View option in DirectSOFT32 will let you view the ladder program as a

DirectSOFT32

flow chart. The figure below shows the symbol convention used in the diagrams. You

may find the stage view useful as a tool to verify that your stage program has

faithfully reproduced the logic of the state transition diagram you intend to realize.

Stage

Reference to

Transition

Jump

S Set Stage

a stage

Logic

R Reset Stage

The following diagram is a typical stage view of a ladder program containing stages.

Note the left-to-right direction of the flow chart.

ISG

DL105 PLC User Manual, 2nd Edition, Rev. A

7-19

RLL^PLUS Stage Programming

RLLPLUS Stage Instructions

Stage

The Stage instructions are used to create

(SG)

structured RLL^PLUS programs. Stages are

program segments which can be activated

by transitional logic, a jump or a set stage

S aaa

that is executed from an active stage.

Stages are deactivated one scan after

transitional logic, a jump, or a reset stage

instruction is executed.

Operand Data Type

DL130 Range

aaa

Stage

0-377

The following example is a simple RLLPLUS Stage program. This program utilizes an

initial stage, and jump instructions to create a structured program.

DirectSOFT32

Handheld Programmer Keystrokes

ISG

ENT

ISG

ENT

STR

ENT

OUT

ENT

STR

SHFT

ENT

SET

RST

SET

ENT

STR

ENT

JMP

ENT

STR

ENT

OUT

ENT

OUT

ENT

STR

ENT

OUT

ENT

STR

SHFT

ENT

AND

RST

OUT

ENT

JMP

DL105 PLC User Manual, 2nd Edition, Rev. A

7-20

RLL^PLUS Stage Programming

Initial Stage

The Initial Stage instruction is normally used

(ISG)

as the first segment of an RLL^PLUS Stage

program. Multiple Initial Stages are allowed

ISG

S aaa

in a program. They will be active when the

CPU enters the Run mode allowing for a

starting point in the program.

Operand Data Type

DL130 Range

aaa

Stage

0-377

Initial Stages are also activated by transitional logic, a jump or a set stage executed

from an active stage.

JUMP

The Jump instruction allows the program to

(JMP)

transition from an active stage containing

S aaa

the jump instruction to another stage

JMP

(specified in the instruction). The jump

occurs when the input logic is true. The

active stage containing the Jump will

deactivate 1 scan later.

Operand Data Type

DL130 Range

aaa

Stage

0-377

In the following example, only stage ISG0 will be active when program execution.

begins. When X1 is on, program execution will jump from Initial Stage 0 to Stage 1.

DirectSOFT

Handheld Programmer Keystrokes

ISG

ENT

ISG

ENT

STR

JMP

ENT

JMP

ENT

STR

OUT

ENT

OUT

ENT

STR

JMP

ENT

JMP

SHFT

ENT

JMP

TMR

JMP

NOTE: The F1-130 CPU does not have the Not Jump instruction (as does other

PLC families). You may still achieve the same result by using the Jump instruction,

while inverting the sense of contact logic that activates that instruction.

DL105 PLC User Manual, 2nd Edition, Rev. A

7-21

RLL^PLUS Stage Programming

Questions and Answers about Stage Programming

We include the following commonly-asked questions about Stage Programming as

an aid to new students. All question topics are covered in more detail in this chapter.

Q. What does stage programming do that I can’t do with regular RLL programs?

A. Stages allow you to identify all the states of your process before you begin

programming. This approach is more organized, because you divide up a ladder

program into sections. As stages, these program sections are active only when they

are actually needed by the process. Most processes can be organized into a

sequence of stages, connected by event-based transitions.

Q. Isn’t a stage really just like a software subroutine?

A. No, it is very different. A subroutine is called by a main program when needed, and

executes just once before returning to the point from which it was called. A stage,

however, is part of the main program. It represents a state of the process, so an

active stage executes on every scan of the CPU until it becomes inactive.

Q. What are Stage Bits?

A. A stage bit is just a single bit in the CPU’s image register, representing the

active/inactive status of the stage in real time. For example, the bit for Stage 0 is

referenced as “S0”. If S0 = 0, then the ladder rungs in Stage 0 are bypassed (not

executed) on each CPU scan. If S0 = 1, then the ladder rungs in Stage 0 are

executed on each CPU scan. Stage bits, when used as contacts, allow one part of

your program to monitor another part by detecting stage active/inactive status.

Q. How does a stage become active?

A. There are three ways:

S If the Stage is an initial stage (ISG), it is automatically active at powerup.

S Another stage can execute a stage JMP instruction naming this stage,

which makes it active upon its next occurrence in the program.

S A program rung can execute a Set Stage Bit instruction (such as Set

S0).

Q. How does a stage become inactive?

A. There are three ways:

S Standard Stages (SG) are automatically inactive at powerup.

S A stage can execute a stage JMP instruction, resetting its Stage Bit to 0.

S Any rung in the program can execute a Reset Stage Bit instruction (such

as Reset S0).

Q. What about the power flow technique of stage transitions?

A. The power flow method of connecting adjacent stages (directly above or below in

the program) actually is the same as the stage Jump instruction executed in the

stage above, naming the stage below. Power flow transitions are more difficult to edit

in DirectSOFT32, we list them separately from two preceding questions.

DL105 PLC User Manual, 2nd Edition, Rev. A

7-22

RLL^PLUS Stage Programming

Q. Can I have a stage which is active for only one scan?

A. Yes, but this is not the intended use for a stage. Instead, just make a ladder rung

active for 1 scan by including a stage Jump instruction at the bottom of the rung.

Then the ladder will execute on the last scan before its stage jumps to a new one.

Q. Isn’t a stage JMP just like a regular GOTO instruction used in software?

A. No, it is very different. A GOTO instruction sends the program execution

immediately to the code location named by the GOTO. A stage JMP simply resets

the stage Bit of the current stage, while setting the stage Bit of the stage named in the

JMP instruction. Stage bits are 0 or 1, determining the inactive/active status of the

corresponding stages. A stage JMP has the following results:

S When the JMP is executed, the remainder of the current stage’s rungs

are executed, even if they reside past(under) the JMP instruction. On

the following scan, that stage is not executed, because it is inactive.

S The stage named in the stage JMP instruction will be executed upon its

next occurrence. If located past (under) the current stage, it will be

executed on the same scan. If located before (above) the current stage,

it will be executed on the following scan.

Q. How can I know when to use stage JMP, versus a Set Stage Bit or Reset Stage Bit?

A. These instructions are used according to the state diagram topology you have

derived:

S Use a stage JMP instruction for a state transition... moving from one

state to another.

S Use a Set Stage Bit instruction when the current state is spawning a

new parallel state or stage sequence, or when a supervisory state is

starting a state sequence under its command.

S Use a Reset Bit instruction when the current state is the last state in a

sequence and its task is complete, or when a supervisory state is

ending a state sequence under its command.

Q. What is an initial stage, and when do I use it?

A. An initial stage (ISG) is automatically active at powerup. Afterwards, it works just

like any other stage. You can have multiple initial stages, if required. Use an initial

stage for ladder that must always be active, or as a starting point.

Q. Can I have place program ladder rungs outside of the stages, so they are always on?

A. It is possible, but it’s not good software design practice. Place ladder that must

always be active in an initial stage, and do not reset that stage or use a stage JMP

instruction inside it. It can start other stage sequences at the proper time by setting

the appropriate stage Bit(s).

Q. Can I have more than one active stage at a time?

A. Yes, and this is a normal occurrence for many programs. However, it is important

to organize your application into separate processes, each made up of stages. And a

good process design will be mostly sequential, with only one stage on at a time.

However, all the processes in the program may be active simultaneously.

DL105 PLC User Manual, 2nd Edition, Rev. A

8-2

Maintenance and Troubleshooting

Hardware System Maintenance

Standard

No regular or preventative maintenance is required for this product (there are no

Maintenance

internal batteries); however, a routine maintenance check (about every one or two

months) of your PLC and control system is good practice, and should include the

following items:

S Air Temperature - Check the air temperature in the control cabinet, so

the operating temperature range of any component is not exceeded.

S Air Filter - If the control cabinet has an air filter, clean or replace it

periodically as required.

S Fuses or breakers - verify that all fuses and breakers are intact.

S DL105 Air Vents - check that all air vents are clear. If the exterior case

needs cleaning, disconnect the input power, and carefully wipe the case

using a damp cloth. Do not let water enter the case through the air vents

and do not use strong detergents because this may discolor the case.

Diagnostics

Your DL105 Micro PLC performs many pre-defined diagnostic routines with every

CPU scan. The diagnostics can detect various errors or failures in the PLC. The two

primary error classes are fatal and non-fatal.

Fatal Errors

Fatal errors are errors which may cause the system to function improperly, perhaps

introducing a safety problem. The CPU will automatically switch to Program Mode if

it is in Run Mode. (Remember, in Program Mode all outputs are turned off.) If the fatal

error is detected while the CPU is in Program Mode, the CPU will not allow you to

transition to Run Mode until the error has been corrected.

Some examples of fatal errors are:

S Power supply failure

S Parity error or CPU malfunction

S Particular programming errors

Non-fatal Errors

Non-fatal errors are errors that need your attention, but should not cause improper

operation. They do not cause or prevent any mode transitions of the CPU. The

application program can use special relay contacts to detect non-fatal errors, and

even take the system to an orderly shutdown or switch the CPU to Program Mode if

desired. An example of a non-fatal error is:

S Particular programming errors

Finding Diagnostic

The programming devices will notify you of an error if one occurs while online.

Information

S DirectSOFT32 provides the error number and an error message.

S The handheld programmer displays error numbers and short

descriptions of the error.

Appendix B has a complete list of error messages in order by error number.

Many error messages point to supplemental V-memory locations which contain

related information. Special relays (SP contacts) also provide error indications.

DL105 PLC User Manual, 2nd Edition, Rev. A

8-3

Maintenance and Troubleshooting

V-memory Error

The following table names the specific memory locations that correspond to certain

Code Locations

types of error messages.

Error Class

Error Category

Diagnostic

V-memory

User-Defined

Error code used with FAULT instruc-

V7751

tion

System Error

Fatal Error code

V7755

Major Error code

V7756

Minor Error code

V7757

Grammatical

Address where syntax error occurs

V7763

Error Code found during syntax check

V7764

CPU Scan

Number of scans since last Program

V7765

to Run Mode transition

Current scan time (ms)

V7775

Minimum scan time (ms)

V7776

Maximum scan time (ms)

V7777

Special Relays (SP) The special relay table also includes status indicators which can indicate errors. For

Corresponding to a more detailed description of each of these special relays refer to Appendix D.

Error Codes

CPU Status Relays

Accumulator Status Relays

SP12

Terminal Run mode

SP60

Acc. is less than value

SP16

Terminal Program mode

SP61

Acc. is equal to value

SP20

STOP instruction was executed

SP62

Acc. is greater than value

SP22

Interrupt enabled

SP63

Acc. result is zero

System Monitoring Relays

SP64

Half borrow occurred

SP40

Critical error

SP65

Borrow occurred

SP41

Non-critical error

SP66

Half carry occurred

SP44

Program memory error

SP67

Carry occurred

SP50

Fault instruction was executed

SP70

Result is negative (sign)

SP51

Watchdog timeout

SP71

Pointer reference error

SP52

Syntax error

SP73

Overflow

SP53

Cannot solve the logic

SP75

Data is not in BCD

SP76

Load zero

DL105 PLC User Manual, 2nd Edition, Rev. A

8-4

Maintenance and Troubleshooting

DL105 Micro PLC These errors can be generated by the CPU or by the Handheld Programmer,

depending on the actual error. Appendix B provides a more complete description of

Error Codes

the error codes.

The errors can be detected at various times. However, most of them are detected at

power-up, on entry to Run Mode, or when a Handheld Programmer key sequence

results in an error or an illegal request.

Error

Description

Error

Description

Code

E003

Software time-out

E526

Unit is offline

E004

Invalid instruction

E527

Unit is online

(RAM parity error in the CPU)

E528

CPU mode

E099

Program memory exceeded

E540

CPU locked

E151

Invalid command

E541

Wrong password

E155

RAM failure

E542

Password reset

E210

Power fault

E601

Memory full

E312

Communications error 2

E602

Instruction missing

E313

Communications error 3

E604

Reference missing

E316

Communications error 6

E620

Out of memory

E320

Time out

E621

EEPROM Memory not blank

E321

Communications error

E622

No Handheld Programmer EEPROM

E501

Bad entry

E624

V memory only

E502

Bad address

E625

Program only

E503

Bad command

E627

Bad write operation

E504

Bad reference / value

E628

Memory type error (should be EEPROM)

E505

Invalid instruction

E640

Mis-compare

E506

Invalid operation

E650

Handheld Programmer system error

E520

Bad operation - CPU in Run

E651

Handheld Programmer ROM error

E524

Bad operation - CPU in Program

E652

Handheld Programmer RAM error

DL105 PLC User Manual, 2nd Edition, Rev. A

DL105 Micro PLC. User Manual (2003) - page 7