GSK 980TC3 Series User manual

Contents
I
The user manual is for GSK980TC3 Series Bus Turning CNC System,
divided into Programming and Operation.
This manual describes the various matters concerning the operations
of this CNC system as much as possible. However, it is impossible to give
detailed descriptions to all the unnecessary or unallowable operations due to
space limitation and product specific applications. Therefore, the matters not
specially described herein should be considered as “impossible” or
“unallowable”.
This user manual is the property of GSK CNC Equipment Co., Ltd.
All rights are reserved. It is illegal for any organization or individual to publish
or reprint this manual. GSK CNC Equipment Co., Ltd. reserves the right to
ascertain their legal liability.

II
Preface
Dear users,
It is our pleasure for your patronage and purchase of this machining center
CNC system of GSK980TC3 Series Bus Turning CNC system produced by GSK
CNC Equipment Co., Ltd.
This book is “Programming and Operation Manual”, which introduces the
programming and operation of GSK980TC3 Series Bus CNC Turning System
(software version V1.4) in detail.
To ensure the product works in a safe and efficient state, please read this
manual carefully before installation and operation.
Warnings
Improper operations may cause unexpected accidents. Only those
qualified staff are allowed to operate this system.
Special notes: The power supply fixed on/in the cabinet is exclusively used for the
CNC system made by GSK.
It cannot be applied for other purposes, or else it may cause serious
danger.

Contents
III
All specifications and designs in this manual are subject to change without notice.
Declaration!
zWe try to describe all the various matters as much as possible in this
manual. However, it is impossible to give detailed descriptions to all
the unnecessary or unallowable operations because there are too
many possibilities. Therefore, the matters not specially described
herein should be considered as “impossible” or “unallowable”.
Warning！
zBefore installing, connecting, programming and operating the product,
please read this manual and the manual provided by the machine tool
builder carefully, and operate the product according to these manuals.
Otherwise, the operation may cause damage to the product and
machine tool, or even cause personal injury.
Caution！
zThe functions and specifications (e.g., precision and speed) described
in this manual are only for this product itself. For those CNC machine
tools installing this product, the actual function configuration and
specifications depend on the designs of the machine tool builders.
Moreover, the function configuration and specifications of the CNC
machine tool are subject to the manual provided by the machine tool
builder.

IV
Safety notes
■ Transportation and storage
zDo not pile up the packing boxes over 6 layers.
zNever climb the packing box, neither stand on it, nor place heavy objects on it.
zDo not move or drag the product by the cables connected to it.
zAvoid impact or scratch to the panel and screen.
zPacking box should be protected from dampness, insolation and drench.
■ Open-package inspection
zConfirm the product is the one you purchased after opening the package.
zCheck whether the product is damaged during transportation.
zConfirm all the elements are complete without damage by referring to the list.
zIf there is incorrect product type, incomplete accessories or damage, please
contact us in time.
■ Connection
zOnly qualified personnel can connect and inspect the system.
zThe system must be earthed. The earth resistance should not be greater than
0.1Ω, and a neutral wire (zero wire) cannot be used as an earth wire.
zThe connection must be correct and secured. Otherwise, the product may be
damaged or unexpected results may occur.
zConnect the surge absorbing diode to the product in the specified direction;
otherwise the product may be damaged.
zTurn off the power before inserting or unplugging a plug, or opening the electric
cabinet.
■ Troubleshooting
zTurn off the power supply before troubleshooting or replacing components.
zOverhaul the system when there is a short circuit or overload, and do not restart
it until the trouble is removed.
zDo not turn ON/OFF the product frequently, and the ON/OFF interval should be 1
minute at least.

Contents
V
Safety Responsibility
Manufacturer Responsibility
——Be responsible for the danger which should be eliminated on the design
and configuration of the provided CNC systems
——Be responsible for the safety of the provided CNC and its accessories
——Be responsible for the provided information and advice
User Responsibility
——Be trained with the safety operation of CNC system operation
procedures and familiar with the safety operation.
——Be responsible for the dangers caused by adding, changing or
modifying the original CNC systems and accessories.
——Be responsible for the danger caused by failing to observe the
operation, maintenance, installation and storage in the manual.
This user manual shall be kept by the end user.
Thank you for your kind support when you are using the products of GSK
CNC Equipment Co., Ltd.

VI
ⅠProgramming
Introduce the technical specification, product type series and parameter
configuration, command code and program format of GSK980TC3 Series Bus
Turning CNC system.
ⅡOperation
Introduce PLC’ operations of GSK980TC3 Series Bus Turning CNC system.
ⅢFunction Description
Introduce the main function of GSK980TC3 Series Bus Turning CNC system.
ⅣInstallation and Connection
Introduce the installation, connection and setting methods of GSK980TC3 Series
Bus Turning CNC system.
Appendix
Introduce the usage of GSK980TC3 Series Bus Turning CNC system matched
with a servo turret.

Contents
VII
CONTENTS
ⅠPROGRAMMING..................................................................................1
CHAPTER 1SEQUENCE PROGRAM CREATING PROCESS .........................................................3
1.1 GSK980TC3 PLC Specification ............................................................................3
1.2 What is a Sequence Program ..................................................................................3
1.3 Distribution Interface (Step 1) ..................................................................................4
1.4 Ladder Diagram Programming (Step 2) .................................................................4
1.5 Sequence Programming Debugging (Step 3)........................................................4
CHAPTER 2SEQUENCE PROGRAM ...........................................................................................5
2.1 Performance Process of Sequence Programming ...............................................5
2.2 The Performance of the Cycle .................................................................................6
2.3 The Priority Sequence of the Performance (the 1st Level, the 2nd level) ........6
2.4 Sequence Programming Structure ..........................................................................8
2.5 The Treatment of the Input/output Signal...............................................................9
2.5.1 Input Signal Treatment ....................................................................................10
2.5.2 The Treatment of the Output Signal.............................................................10
2.5.3 The Distinguish of the Signal State Between the 1st Level and the
2nd Level Program ........................................................................................................10
2.6 Interlocking..................................................................................................................11
CHAPTER 3PLCADRRESS .....................................................................................................13
3.1 Machine →PLC addressX...........................................................................13
3.1.1 X Address on the I/O Input...............................................................................14
3.1.2 X Address on the MDI Panel ...........................................................................14
3.2 PLC →Address of the Machine Tool Side (Y)...................................................15
3.2.1 Y Address on the MDI Panel...........................................................................15
3.3 PLCCNC AddressG.....................................................................................16
3.4 CNC→PLC AddressF......................................................................................16
3.5 Internal Replay AddressR...............................................................................17
3.6 Nonvolatile Relay Address（K）...........................................................................17
3.7 Information Display Request Address（A）........................................................18
3.8 Counter TimerC................................................................................................18
3.9 Counter Preset Value AddressDC.................................................................18
3.10 Timer AddressT................................................................................................19
3.11 Presetting Value Address of the TimerDT....................................................19
3.12 Data Table AddressD.......................................................................................19
3.13 Sign AddressL..................................................................................................19
3.14 Subprogram NumberP....................................................................................19
CHAPTER 4PLC BASIC CODES..............................................................................................21
4.1 RD, RD.NOT, WRT, and WRT.NOT Codes............................................................21
4.2 AND, AND.NOT Code ...............................................................................................22

VIII
4.3 OR, OR.NOT Code....................................................................................................22
4.4 OR. STK Code ...........................................................................................................23
4.5 AND.STK Code ..........................................................................................................23
CHAPTER 5PLC FUNCTIONAL CODE ....................................................................................25
5.1 END1（1st Level Sequence Program End）.......................................................25
5.2 END2（2nd level sequence program end）.........................................................26
5.3 CALL（call subprogram）......................................................................................26
5.4 CALLUUnconditional Subprogram Call........................................................27
5.5 SPSubprogram.................................................................................................27
5.6 SPESubprogram End......................................................................................28
5.7 SETSet..............................................................................................................28
5.8 RSTReset..........................................................................................................29
5.9 JMPBLabel Jump.............................................................................................29
5.10 LBL（Label）...........................................................................................................30
5.11 TMRTimer.........................................................................................................30
5.12 TMRBFixed Timer............................................................................................31
5.13 TMRCTimer......................................................................................................32
5.14 CTRBinary Counter.........................................................................................33
5.15 DECBinary Decode.........................................................................................35
5.16 CODBinary Code Conversion........................................................................36
5.17 COM (Common Line Control)................................................................................37
5.18 COME (Common Line Control End).....................................................................38
5.19 ROTBinary Rotation Control..........................................................................38
5.20 SFTShift Register............................................................................................41
5.21 DIFURising Edge Check................................................................................42
5.22 DIFDFalling Edge Check................................................................................43
5.23 COMPBinary Comparison..............................................................................43
5.24 COINCoincidence Check...............................................................................44
5.25 MOVNTransfer of Data...................................................................................45
5.26 MOVBTransfer of One Byte...........................................................................46
5.27 MOVWTransfer of Two-Byte..........................................................................47
5.28 XMOV（Binary Index Modifier Data Transfer）.................................................47
5.29 DSCH Binary Data Search............................................................................48
5.30 ADDBinary Addition.........................................................................................50
5.31 SUB（Binary Subtraction）...................................................................................51
5.32 ANDFFunctional And......................................................................................52
5.33 ORFFunctional Or...........................................................................................53
5.34 NOTLogical Not...............................................................................................54
5.35 EORexclusive or..............................................................................................55
CHAPTER 6LADDER WRITING LIMIT....................................................................................57
ⅡOPERATION .......................................................................................59
CHAPTER 1PLC INTERFACE DISPLAY...................................................................................61
1.1 Automatic Operation when GSK980TC3 PLC Power on ..................................61

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IX
1.2 INFO interface display.............................................................................................61
1.2.1 INFO interface ..................................................................................................61
1.2.2 PLCGRA Interface...........................................................................................62
1.2.3 PLCPAR Interface............................................................................................63
1.2.4 PLCDGN Interface...........................................................................................64
1.2.5 PLCTRA Interface............................................................................................65
CHAPTER 2PLCADDRESS,PARAMETER SETTING................................................................69
2.1 Nonvolatile/Hold Relay............................................................................................69
2.2 Timer ..........................................................................................................................70
2.3 Data List.....................................................................................................................71
2.4 Counter ......................................................................................................................72
CHAPTER 3INSTRUCTIONS OF THE LADDER DIAGRAM EDIT SOFTWARE............................75
3.1 Summary ...................................................................................................................75
3.2 Software Introduction...............................................................................................75
3.2.1 Software Start.....................................................................................................75
3.2.2 Function Introduction ..........................................................................................76
3.3 Software Operation..................................................................................................77
3.3.1 Toolbar .................................................................................................................77
3.3.2 Selecting a Figure ...............................................................................................79
3.3.3 Editing a Figure ...................................................................................................79
3.3.4 Ladder Diagram Note.............................................................................................81
3.3.5 Export .......................................................................................................................82
III FUNCTION.........................................................................................85
CHAPTER 1CONTROLLED AXIS .............................................................................................87
1.1 Output Signal of Controllable Axis.........................................................................87
1.2 Output of Axis Movement State .............................................................................87
1.3 Servo Ready Signal .................................................................................................88
CHAPTER 2PREPARATION FOR OPERATION .........................................................................89
2.1 Emergency stop .......................................................................................................89
2.2 CNC Overtravel Signal............................................................................................89
2.3 Alarm Signal..............................................................................................................90
2.4 Operation Mode Selection ......................................................................................91
2.5 Status Output Signal................................................................................................92
CHAPTER 3MANUAL OPERATION..........................................................................................93
3.1 JOG Feed/Incremental Feed..................................................................................93
3.2 MPG / Step Feed......................................................................................................94
CHAPTER 4REFERENCE POINT RETURN ...............................................................................95
4.1 Manual Reference Point Return ............................................................................95
CHAPTER 5AUTOMATIC OPERATION....................................................................................97
5.1 Cycle Start/Feed Hold .............................................................................................97
5.2 Reset..........................................................................................................................98
5.3 Testing a Program....................................................................................................99
5.3.1 Machine Tool Lock..........................................................................................99
5.3.2 Dry Run ............................................................................................................100

X
5.3.3 Single Block ...................................................................................................100
5.4 Optional Block Skip ...............................................................................................101
CHAPTER 6FEEDRATE CONTROL........................................................................................103
6.1 Rapid Traverse Rate .............................................................................................103
6.2 Feedrate Override..................................................................................................103
6.3 Override Cancel .....................................................................................................104
CHAPTER 7MISCELLANEOUS FUNCTION ............................................................................105
7.1 M code Miscellaneous Function ..........................................................................105
7.2 S Code Miscellaneous Function..........................................................................107
7.3 T Code Miscellaneous Function ..........................................................................108
7.4 Miscellaneous Function Strobe Signal ...............................................................108
7.5 Auxiliary Function Lock.........................................................................................109
CHAPTER 8SPINDLE SPEED FUNCTION ................................................................................111
8.1 Spindle Speed Control Mode ................................................................................. 111
8.1.1 Gear Spindle..................................................................................................... 111
8.1.2 Analog Spindle ................................................................................................ 111
8.2 PMC Axis Control Mode.......................................................................................... 113
8.2.1 Signal Address ................................................................................................ 114
8.2.2 Command......................................................................................................... 115
8.2.3 Command Operaton Time Diagram ........................................................... 115
8.2.4 Signal Explanation ......................................................................................... 115
8.3 Cs Contour Control Mode....................................................................................... 117
8.3.1 Cs Contour Controlled Axis Setting .......................................................... 117
8.3.2 Switch Spindle Rotation Control/Cs Contour Control............................. 117
8.3.3 Axis Setting of Cs Contour Controlled Axis Executing Interpolation118
8.3.4 Cs Contour Controlled Axis’ Reference Point Return .......................... 118
8.3.5 Cs Contour Controlled Axis’ Run (Auto/Manual) ................................... 118
CHAPTER 9PROGRAMMING CODE ......................................................................................121
9.1 Custom Macro Program........................................................................................121
CHAPTER 10 DISPLAY/SET ...................................................................................................123
10.1 Clock Function .....................................................................................................123
10.2 Displaying Operation History .............................................................................123
10.3 Help Function .......................................................................................................123
CHAPTER 11 MEASUREMENT...............................................................................................125
CHAPTER 12 PANEL LOCKED SETTING ...............................................................................127
ⅣINSTALLATION AND CONNECTION...........................................137
CHAPTER 1SYSTEM STRUCTURE AND INSTALLATION ........................................................139
1.1 System Composition ...............................................................................................139
1.2 System Installation & Connection .........................................................................139
1.3 CNC System Installation Dimension.....................................................................140
1.4 Additional Panel ......................................................................................................141
CHAPTER 2DEVICE CONNECTION.......................................................................................145
2.1 CNC External Connection ......................................................................................145
2.1.1 Interface Layout ..............................................................................................145

Contents
XI
2.1.2 Bus Servo Connection Diagram ...............................................................146
2.2 Connection between the System and the Drive Unit..........................................147
2.2.1 System Interface Drawing.............................................................................147
2.2.2 Signal Explanation..........................................................................................147
2.2.3 GSK-LINK Cable Connection Drawing ......................................................149
2.3 RS232 Standard Serial Interface ...........................................................................151
2.4 Connection between MPG and Handhold Unit ...................................................151
2.4.1 Interface Signal Diagram...............................................................................151
2.4.2 Introduction of Interface Signals ................................................................152
2.4.3 Handhold Unit’s Interface Circuit ...............................................................154
2.5 System Power Supply Interface.............................................................................155
2.6 Connection of the Spindle Encoder.......................................................................155
2.6.1 Interface Signal Introduction .......................................................................156
2.6.2 Cable Connection Diagram ..........................................................................157
2.7 GL200 Bus Module Overboard Connection Diagram ........................................157
2.7.1 X Address Definition Input ...........................................................................159
2.7.2 Y Address Definition Output ........................................................................161
2.8 Connection of Spindle Unit .....................................................................................162
2.8.1 Interface Signal Diagram...............................................................................162
2.8.2 Spindle Interface Definition..........................................................................162
2.8.3 Cable Connection Diagram ..........................................................................163
CHAPTER 3MACHINE CONTROL I/O INTERFACE................................................................165
3.1 Interface Signal Diagram ........................................................................................165
CHAPTER 4MACHINE DEBUGGING......................................................................................167
4.1 Debug Preparation...................................................................................................167
4.2 System Power-on.....................................................................................................167
4.3 Emergency Stop and Limit......................................................................................168
4.4 Changing the Gear Ratio ........................................................................................169
4.5 Backlash Compensation .........................................................................................170
4.6 Settings relevant to the Drive Unit.........................................................................172
4.7 The Machine Screw Pitch Compensation ............................................................173
4.8 Mechanical Zero Return (Machine Zero Return) ................................................178
4.8.1 Bus Servo Zero Return Function Setting .................................................178
4.9 The Spindle Rotation (CW/CCW) Input/Output Signal Control.........................183
4.10 The Spindle Gear Change Control......................................................................184
4.11 The External Cycle Start and Feed Hold............................................................185
4.12 Cooling, Lubricating Control.................................................................................186
4.13 Setting the Relative Feedrate ..............................................................................186
4.14 Chuck Control.........................................................................................................188
4.15 Tool Change Control..............................................................................................190
4.16 Tailstock Control.....................................................................................................191
4.17 C/S Axis Control .....................................................................................................192
4.18 Setting Related to the 4th Axis..............................................................................193
4.19 Relevant Bus Servo Setting .................................................................................194

XII
APPENDIX ................................................................................................196
APPENDIX 1 SERVO TOOL POST EXPLANATION ......................198
1. Software Version Information ...........................................................................198
2. Relevant Signal Parameter to the CNC System ...........................................198
3. Functional description...........................................................................................201
4. Flow chart and I/O input/output control............................................................201
APPENDIX 2 TAIWAN LIUXIN TOOL POST WIRE TABLE ..........205
APPENDIX 3 LADDER CONFIGURATION FILE FORMAT...........207
1. F Signals and meanings of M code M00---M99 ...............................................207
2. “%” that occupies a line exclusively means the end of M code
information storage. ...................................................................................................207
3. The codes and meanings of X signal X0.0-X6.7..............................................207
4. The codes and meaning of Y signal Y0.0---Y5.7 .............................................207
5. The codes and meanings of K signal Y6.0---Y63.7.........................................207
6. The codes and meanings of A signal A0.0-A31.7A ........................................208
7. end // end sign..........................................................................................................208
APPENDIX 4 COMMON DEBUGGING METHOD...........................209
1.1 Zero Return Method and Common Parameter Setting......................................209
1.2 Chuck Control...........................................................................................................212
1.3 Tailstock Control.......................................................................................................213
1.4 Hydraulic Start ..........................................................................................................213
1.5 Cs Axis Setting .........................................................................................................213

1
Programming
Programming

GSK980TC3 Series Bus Turning CNC system PLC, Installation and Connection User Manual
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Programming

Chapter 1 Sequence Program Creating Process
3
一
Programming
Chapter 1 Sequence Program Creating Process
1.1 GSK980TC3 PLC Specification
GSK980TC3 PLC is shown below:
Table 1-1-1
1.2 What is a Sequence Program
The programming is performed a logic control to the machine tool and its relative equipments, which
is called sequence programming.
After the programming is converted into some kind of format, CPU can be performed the code and
calculation treatment for it, and its fruits can be memorized to RAM. CPU can be rapidly read each
code stored in the memory, which can be performed the programming according to the calculation
operation.
The compiling of the sequence programming starts with developing of the ladder diagram.
Specification GSK980TC3 PLC
Programming language Ladder
Program level 2
The 1st level program execution cycle 8ms
Basis code average treatment time 5μs
Programming capacity 8000 steps
Code Basis code + function code
Internalrelay (R)
PLC alarm detection (A)
Nonvolatile memory area
Timer （T）
Counter (C)
Database (D)
Nonvolatilerelay (K)
Counter prevalue data register (DC)
Timer prevalue data register (DT)
Subprogram (P)
Mark (L)
Input signal of NC side (F)
Signal outputs to the NC side (G)
0~990 （byte）
0~63（byte）
0~127 （byte ）
0~127 （word）
0~255 （word）
0~63 （byte ）
0~127（word）
0~127（word）
0~99
0~99
0～255（byte ）
0～255（byte ）
I/O module （X）
（Y）
0~127 （byte ）
0~127 （byte ）

GSK980TC3 Series Bus Turning CNC system PLC, Installation and Connection User Manual
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Programming
1.3 Distribution Interface (Step 1)
The interface can be distributed after confirming the controlled object and calculating the
points of the corresponding input/output signal.
Refer to the Chapter Four Input/output interface signal table in the part of the Installation and
Connection when distributing the interface.
1.4 Ladder Diagram Programming (Step 2)
GSK980TC3 ladder diagram is not permitted by an on-line modification but is edit by the
software Lad Edit.exe on the computer. The control operation required by the machine tool can be
expressed by the ladder diagram. The functions, such as the timer and counter, can not be
expressed by relay symbols, which can be indicated by the specified function code symbols.
The compiled ladder diagram should be upgraded to the system.
1.5 Sequence Programming Debugging (Step 3)
The sequence programming can be debugged using the following methods:
1) Debugging with emulator
The machine tool can be replaced by an emulator (it composes of the lights and switches).
The input signal state of the machine tool can be expressed by the ON or OFF of the switches;
and the output signal state can be indicated by the ON or OFF of the light.
2) Debugging with actual operation
Debug on the actual machine tool. It is better to prepare the precautions before debugging,
due to an unexpected behavior may occur.

Chapter 2 Sequence Program
5
Programming
Chapter 2 Sequence Program
The operating principle is different with the common relay, because the PLC sequence
controlling is carried out by the ladder diagram Lad Edit.exe compiling.
And therefore, it is better to thoroughly understand the sequence controlling principle when
designing the PLC sequence programming.
2.1 Performance Process of Sequence Programming
In the general relay controlling circuits, each of them can be simultaneously operated. When the
relay A is operated in the following figure, the replay D and E can be operated (when the contactor A
and B are closed) at the same. Each replay in the PLC sequence control is operated in turn. The
relay D is operated before relay A, and then the relay E operates (refer to the following figure).
Namely, each relay is operated based upon the sequence of the ladder diagram (compiling
sequence).
A
A
B
C
D
E
Fig. 2.1 (a) Circuit illustration
The differences between the relay circuit and PLC programming operation are shown below in the
Fig. 2.1 (b) and Fig. 2.1 (c).
A
A
C
B
C
Fig. 2.1 (b)

GSK980TC3 Series Bus Turning CNC system PLC, Installation and Connection User Manual
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Programming
A
AC
C
B
Fig. 2.1 (c)
(1) Relay circuit
Both Fig. 2.1 (b) and Fig. 2.1 (c) are shared a same operation. B and C are switched on after A is
turned on. B is cut off after C is ON.
(2) PLC program
A same relay is shared a same circuit, refer to the Fig. 2.1 (b); B and C are switched on after A is
turned on. B is cut off after one cycle of the PLC program is performed. In the Fig. 2.1 (c), C is ON
instead of B, after C is turned on.
2.2 The Performance of the Cycle
PLC performs from the beginning to the end of the ladder diagram. It performs again from the
beginning of the ladder diagram after this diagram is performed, which is called cycle performance.
The performance time from the beginning to the end of the ladder diagram is abbreviated as a
period of a cycle treatment. The shorter of the treatment period is, the stronger of the response
capacity of the signal is.
2.3 The Priority Sequence of the Performance (the 1st Level, the
2nd level)
GSK980TC3 PLC program are composed of two parts: the 1st level program and the 2nd level
program, which are inconsistent with the performance period.
The 1st level program performs once each 8ms, which can be treated some fast corresponding and
short pulse.

Chapter 2 Sequence Program
7
Programming
The 2nd program performs once each 8*nms. N is the partition value of the 2nd level program.
PLC may divide the 2nd level program into N parts when the 2nd level program is executed. It is
performed one part for each 8ms.
Fig. 2-3-1
PLC in the GSK980TC3 is separately performed in the PLC-AVR SCM. The 1ms of each 8ms is the
communication time for reading the PLC data from the CNC. The 5ms is that the PLC gains the
system control signal (F. X), and uploads the control result data (G, Y parameter) external port I/O.
PLC is always performed the ladder diagram calculation other than the interruption of the response
exchange data.
Fig. 2-3-2
When the last partition value of the 2nd level program of the n is performed, the program is then
executed from the beginning of the program. In this case, when the partition value is n, the
performance time of one cycle is 8*n ms. The 1st level program performs once each 8ms; the 2nd level
program performs once each 8*n ms. If its steps of the 1st level program is increased, and therefore
the steps of the 2nd level program within 8ms should be reduced correspondingly; the partition value
may be increased, and the treatment time of the overall program will be longer. So, the compiling of
the 1st level program should be shorter.

GSK980TC3 Series Bus Turning CNC system PLC, Installation and Connection User Manual
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Programming
2.4 Sequence Programming Structure
The ladder diagram is compiled with sequence in the traditional PLC. It owns the following
advantages in the ladder diagram language allowing the structured programming:
1. The program is easy to comprehend and compile.
2. It is more convenient to find the faults during the programming.
3. It is easy to find some reasons when the operation malfunction occurs.
The methods of the main structure programming are shown below:
1) Sub-program
The subprogram is regarded as a treatment unit based on the ladder diagram.
Task A
Task B
A
A
C
B
C
.
.
.
.
Fig. 2-4-1
2) Nesting
One subprogram can be performed the task by calling another one.
Task A
Task B
Main program
Task A1
Task An
Task A11
Task A12
Subprogram 1 Subprogram 2
Fig. 2-4-2
3) Conditional branch
The main program is performed circularly, and checks whether its conditions are suitable. The
corresponding subprograms are performed under these conditions, vice versa.