Iec 61131-3 Second edition 2003-01 Programmable controllers – Part 3: Programming languages

Figure 21 a) - Synchronization of function blocks with explicit task associations
IEC 2496/02
Copyright International Electrotechnical Commission 
Provided by IHS under license with IEC
Not for Resale
No reproduction or networking permitted without license from IHS
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---

61131-3 
 IEC:2003(E)
– 121 –
RESOURCE R1
fast1
+----------+
| TASK |
t#10ms---|INTERVAL |
1---|PRIORITY |
+----------+
slow1
+----------+
| TASK |
t#20ms---|INTERVAL |
2---|PRIORITY |
+----------+
P1
PROGRAM X
Y1 Y2
+-----+ +-----+
| Y | | Y |
---|A C|----+--------|A C|---
---|B D|----|--+-----|B D|---
+-----+ | | +-----+
|fast1| | |
+-----+ | |
| |
| | Y3
| | +-----+
| | | Y |
+--|--|A C|---
+--|B D|---
+-----+
END_PROGRAM
slow1
Figure 21 b) - Synchronization of function blocks with implicit task associations
IEC 2497/02
Copyright International Electrotechnical Commission 
Provided by IHS under license with IEC
Not for Resale
No reproduction or networking permitted without license from IHS
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---

– 122 –
61131-3 
 IEC:2003(E)
RESOURCE R1
fast1
+----------+
| TASK |
t#10ms---|INTERVAL |
1---|PRIORITY |
+----------+
slow1
+----------+
| TASK |
t#20ms---|INTERVAL |
2---|PRIORITY |
+----------+
P1
PROGRAM X
Y1 Y2
+-----+ +-----+
| Y | | Y |
---|A C|----+--------|A C|---
---|B D|----|--+-----|B D|---
+-----+ | | +-----+
|fast1| | | |slow1|
+-----+ | | +-----+
| |
| | Y3
| | +-----+
| | | Y |
+--|--|A C|---
+--|B D|---
+-----+
|slow1|
+-----+
END_PROGRAM
Figure 21 c) - Explicit task associations equivalent to figure 21 b)
IEC 2498/02
Copyright International Electrotechnical Commission 
Provided by IHS under license with IEC
Not for Resale
No reproduction or networking permitted without license from IHS
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---

61131-3 
 IEC:2003(E)
– 123 –
3 Textual languages
The textual languages defined in this standard are IL (Instruction List) and ST (Structured Text). The
sequential function chart (SFC) elements defined in 2.6 can be used in conjunction with either of these
languages.
3.1 Common elements
The textual elements specified in clause 2 shall be common to the textual languages (IL and ST)
defined in this clause. In particular, the following program structuring elements shall be common to
textual languages:
TYPE...END_TYPE
(2.3.3)
VAR...END_VAR
(2.4.3)
VAR_INPUT...END_VAR
(2.4.3)
VAR_OUTPUT...END_VAR
(2.4.3)
VAR_IN_OUT...END_VAR
(2.4.3)
VAR_EXTERNAL...END_VAR
(2.4.3)
VAR_TEMP...END_VAR
(2.4.3)
VAR_ACCESS...END_VAR
(2.4.3)
VAR_GLOBAL...END_VAR
(2.4.3)
VAR_CONFIG...END_VAR
(2.4.3)
FUNCTION ... END_FUNCTION
(2.5.1.3)
FUNCTION_BLOCK...END_FUNCTION_BLOCK
(2.5.2.2)
PROGRAM...END_PROGRAM
(2.5.3)
STEP...END_STEP
(2.6.2)
TRANSITION...END_TRANSITION
(2.6.3)
ACTION...END_ACTION
(2.6.4)
3.2 Instruction list (IL)
This subclause defines the semantics of the IL (Instruction List) language whose formal syntax is
given in B.2.