The document discusses different types of programming languages used in programmable logic controllers (PLCs), including ladder logic, Boolean logic, and Grafcet. It provides details on each language and describes common instruction sets used, such as timers, counters, arithmetic, and data manipulation. The document also covers IEC 61131-3 standard languages like ladder diagrams, function block diagrams, instruction lists, structured text, and sequential function charts. Finally, it discusses PLC architecture and different I/O bus network standards and configurations.

1. 1

2. TYPES OF PLC LANGUAGES
The three types of programming languages used in
PLCs are:
• Ladder
• Boolean
• Grafcet
2

3. LADDER LANGUAGE
3

4. Enhanced functional block format
4

5. PLC Instruction Set Classifications
5

6. These instruction categories include:
• ladder relay
• timing
• counting
• program/flow control
• arithmetic
• data manipulation
• data transfer
• special function (sequencers)
• network communication
6

7. BOOLEAN
Some PLC manufacturers use Boolean language, also called
Boolean mnemonics, to program a controller.
7

8. GRAFCET
•Grafcet (Graphe Fonctionnel de Commande Étape
Transition) is a symbolic, graphic language, which
originated in France, that represents the control
program as steps or stages in the machine or process.
•In fact, the English translation of Grafcet means “step
transition function charts.”
•As the IEC 1131 standard’s sequential function charts
(SFCs), which allow several PLC languages to be used in
one control program.
8

9. 9

10. Grafcet translation
10

11. LADDER DIAGRAM FORMAT
•A ladder rung is TRUE when it has logic continuity.
•Logic continuity exists when power flows through the rung
from left to right.
•The execution of logic events that enable the output provide
this continuity.
11

12. Illustration of several different continuity
paths in a ladder rung
12

13. Monitoring device showing
(a)Power continuity through the rung—inputs 11 and 12 are
ON, turning output 40 ON.
(b)Power continuity through only input 12, thus output 40 is
not ON.
13

14. Functional block instructions
(a) one enable line and one output
(b) one enable line, a start timing command, and two outputs.
14

15. A functional block instruction that is always enabled
To make a block active at all times without any driving logic, the
user can omit all contact logic and place a continuity line in the
block during programming
15

16. The ladder rung matrix
•It determines the maximum number of ladder contact
elements that can be used to program a rung.
•The size of this matrix differs among both PLC manufacturers
and the programming devices used
16

17. Ladder matrix
(a)functional block instructions
(b)Enhanced ladder format functional instructions.
17

18. •One rule, which is present in almost all PLCs, prevents
reverse (i.e., right-to-left) power flow in a ladder rung.
•PLC logic does not allow reverse power to avoid sneak
paths.
•Sneak paths occur when power flows in a reverse
direction through an undesired field device, thus
completing a continuity path.
•If a PLC’s logic requires reverse power flow, the user
must reprogram the rung with forward power flow to
all contact elements.
18

19. 19

20. 20

21. EXAMINE-ON/NORMALLY OPEN EXAMINE-OFF/NORMALLY CLOSED
21

22. OUTPUT COIL
22

23. LATCH/UNLATCH OUTPUT COIL
23

24. ONE-SHOT OUTPUT
24

25. TRANSITIONAL CONTACT
25

26. Ladder rung where all outputs
turn ON in the same scan
26

27. Ladder rung where the outputs
turn ON in different scans
27

28. TIMER INSTRUCTIONS
28

29. 29

30. Hardwired circuit with time-delay
and instantaneous contacts
30

31. ON-DELAY ENERGIZE/ DE-ENERGIZE TIMER
31

32. OFF-DELAY ENERGIZE/ DE-ENERGIZE TIMER
32

33. COUNTER INSTRUCTIONS
33

34. Counter function block with
up, down, and reset counter
instructions
34

35. Automatically resetting counter
35

36. Program/flow control instructions
•They direct the flow of operations, as well as
the execution of instructions, within a ladder
program.
•They perform these functions using branching
and return instructions, which are executed
when certain already programmed control logic
conditions occur.
36

37. 37

38. 38

39. Example of an MCR instruction
39

40. Example of a jump to instruction
40

41. PLC with assigned subroutines at
the end of the program
41

42. User-created subroutine area
42

43. ARITHMETIC INSTRUCTIONS
43

44. Arithmetic Instructions
(a) Coil (b) contact (c) block format.
44

45. DATA MANIPULATION INSTRUCTIONS
45

46. DATA TRANSFER INSTRUCTIONS
46

47. SPECIAL FUNCTION INSTRUCTIONS
47

48. A sequencer (SEQ) block
48

49. Sequencer instruction block
49

50. DIAGNOSTICS
A diagnostics (DIAG) block instruction compares two
memory blocks.
50

51. PID functional block
51

52. 52

53. Operation of a network output coil and a network
contact instructions.
Note that contact 20 in PLC #2 is a local contact
53

54. Network Send/Receive
54

55. BOOLEAN MNEMONICS
It is a PLC language based primarily on the Boolean operators
AND, OR, and NOT.
55

56. INTRODUCTION TO THE IEC 1131
The International Electrotechnical Commission
(IEC) SC65B-WG7 committee developed the IEC
1131 standard in an effort to standardize
programmable controllers.
One of the committee’s objectives was to
create a common set of PLC instructions that
could be used in all PLCs.
56

57. It defines two graphical languages and two text-based
languages for use in PLC programming.
The graphical languages use symbols to program control
instructions, while the text-based languages use
character strings to program instructions.
Graphical languages
• ladder diagrams (LD)
• function block diagram (FBD)
Text-based languages
• instruction list (IL)
• structured text (ST)
57

58. The five IEC 61131-3 Programming languages
Function Block Diagram (FBD) graphical languages Sequential Flow Chart (SFC)
AUTO CALC1
START STEP
DI CALC PUMP
V IN1 OUT >=1 DO T1
MAN_ON V N ACTION D1 D1_READY
STEP A
ACT IN2
D ACTION D2 D2_READY
T2
N ACTION D3 D3_READY
STEP B
Ladder Diagram (LD)
D ACTION D4 D4_READY
CALC1 T3
AUTO CALC PUMP
IN1 OUT
ACT textual languages Structured Text (ST)
IN2
VAR CONSTANT X : REAL := 53.8 ;
MAN_ON
Z : REAL; END_VAR
VAR aFB, bFB : FB_type; END_VAR
bFB(A:=1, B:=„OK‟);
Instruction List (IL) Z := X - INT_TO_REAL (bFB.OUT1);
A: LD %IX1 (* PUSH BUTTON *) IF Z>57.0 THEN aFB(A:=0, B:=“ERR”);
ANDN %MX5 (* NOT INHIBITED *) ELSE aFB(A:=1, B:=“Z is OK”);
ST %QX2 (* FAN ON *) END_IF
58

59. 59

60. Limit switch addressed
(a) a standard PLC environment (b) an IEC 1131-3 environment
60

61. •Ladder diagram language (LD) uses a
standardized set of ladder programming
symbols to implement control functions.
•Instruction list (IL) is a low-level language
similar to the machine or assembly language
used with microprocessors. This type of
language is useful for small applications, as well
as applications that require speed optimization
of the program or a specific routine in the
program.
61

62. 62

63. •Structured text (ST) is a high-level language that allows
structured programming, meaning that many complex
tasks can be broken down into smaller ones. ST
resembles a BASIC- or PASCAL-type computer language.
Structured text programming is particularly suited to
applications involving data handling, computational
sorting, and intensive mathematical applications
utilizing floating-point values.
ST is also the best language for implementing artificial
intelligence (AI) computations, fuzzy logic, and decision
making.
63

64. 64

65. SEQUENTIAL FUNCTION CHARTS (SFC)
Sequential functional chart, or SFC, is a graphical
“language” that provides a diagrammatic
representation of control sequences in a program.
Basically, sequential function chart is a flowchart-
like framework that can organize the subprograms
or subroutines (programmed in LD, FBD, IL, and/or
ST) that form the control program.
65

66. The SFC programming framework contains three main
elements that organize the control program:
• steps
A step is a stage in the control process.
• transitions
After the PLC executes a step/action, it must receive
a transition before it will proceed to the next step.
• actions
Each step may or may not have an action associated
with it. An action is a set of control instructions
prompting the PLC to execute a certain control
function during that step.
66

67. Sequential function chart of
a mixing process
67

68. Comparison of an SFC
diagram and a flowchart
68

69. Macrostep within an SFC program
69

70. Graphic symbols used in SFCs
70

71. (a) Level 1 SFC level 2 SFC
71

72. PROGRAMMING NORMALLY
CLOSED TRANSITIONS
72

73. DIVERGENCES AND CONVERGENCES
A divergence is when an SFC element has many links going out of
it, while a convergence is when an element has many links
coming into it.
73

74. OR Divergences and Convergences
74

75. AND Divergences and Convergences
75

76. 76

77. General PLC architecture
RS 232 Ethernet
Real-Time flash serial port ethernet
CPU ROM
Clock EPROM controller controller
extension
bus
parallel bus buffers
fieldbus analog- digital- external
Digital
controller digital analog Digital Output I/Os
Input
converters converters
signal power signal
relays
conditioning amplifiers conditioning
field bus direct Inputs and Outputs
77

78. I/O bus network block diagram
78

79. Connection between a PLC, a local area
network, and an I/O bus network
79

80. TYPES OF I/O BUS NETWORKS
I/O bus networks can be separated into two different
categories—one that deals with low-level devices that
are typical of discrete manufacturing operations and
another that handles high-level devices found in
process industries.
These bus network categories are:
• device bus networks
• process bus networks
80

81. I/O bus network classification diagram
81

82. Network and protocol standards
82

83. InterBus-S I/O network interface
connected to a Siemens PLC
83

84. An InterBus-S network with a
host controller interface to a PLC
84

85. ASI bit-wide device bus network
85

86. I/O bus network using the
CANbus and ASI networks
86

87. Process bus configuration
87

88. Bridge connecting low-speed and
high-speed Fieldbus networks
88

89. Profibus hierarchy
89

90. DeviceNet I/O bus port connections
90

91. 91

92. 92