老外写的ST语言教程-很详细.ppt
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1、1,ST Language,Basic Course,2,ST Language,Key wordIf there is any unclear or uncorrected,please feel free to speak out,Basic Course,3,Requirements,HardwareThe programming language ST is only available for following programmable controllers:,pCO3 Supernode pCO5 pCO compact,BIOSTo support ST language,b
2、ios version must greater than 5.0,Software,4,Creation of a solution ST Language,Choosing:-FBD,the application will be mixed,it will consist of a main with Atoms,Macroblocks.but you can use routines(functions and function blocks)written in the ST-ST,the application will be developed entirely using ST
3、 language,5,Basic concepts,When programming in ST,the application can be organised using three fundamental programming elements generically called Program Organization Units(POU):PROGRAM FUNCTION FUNCTION BLOCK,POU,Note:we can define more functions and function blocks,but only one program main,6,The
4、 basic types,The following table lists all the properties of basic types(IECType):,7,Declaration of Global variables,There are two ways to declare Global variables:Variable ListTextual mode of ST language,Note:if you want to see the variable in the pGD,please declare the variable in the Variable Lis
5、t,8,Assignment operator:=,Syntax,Assign to a variable:,a constant value the value of another variable the result of an expression.,Varaible_name:=expression;,Note:there is a;in the end of statement,9,Textual declaration,To declare variables in ST you have to use the following declaration block:,Note
6、:1.there is no;in the end of END_VAR;2.we can give the default value in the declaration.,10,Rules of the identifiers(variables name),a.z,A.Z 0.9 _,The name of an identifier(variable or constant)can be any combination(see Example)of the characters listed below:,ExampleRules to create identifiers.,11,
7、The qualifier CONSTANT,Textual declaration of Constants,The keyword CONSTANT can declare a constant.The constants do not occupy space in memory as the variables During compilation instead of the constant is replaced a numeric value.,12,Comments,Comment using keyword REGION ENDREGIONYou can hide seve
8、ral lines of code using the keyword REGION ENDREGION.So increase the readability of the code on the screen.The code is replaced with a comment.Clicking on comment it will appear again the code.,The code commentsYou can use two ways to make a commentTo comment a single code line use“”To comment more
9、code lines use“(*”and“*)”,There is no _ in between END and REGION,13,The qualifier RETAIN,Textual declaration of global variables REATAIN(retentive),Example,Declaration of retentive Global variables.,RETAIN keyword declares a variable in T-permanent memory.,Organization of the variables.,Note:pay at
10、tention of the default value,14,Cast Functions,Syntax,Variable_name:=*_TO_*(value);,The conversion functions are used to convert any of the elementary data types to any other.They must be used to make the data type uniform before a function,where this is required.,15,ST operators,For the evaluation
11、of expressions,always use brackets,this avoids errors in the evaluation of the expressions.,Example,Table of the operators priority,An expression is executed only after the evaluation of the operators priority.The execution order of an expression and its result are influenced by the operators priori
12、ty.,Suggestion,A:=NOT X AND Y OR NOT J;Increases readability:A:=NOT(X)AND(Y OR(NOT J);,If Z=0 the other variables have not been evaluated.A:=Z AND Y AND(NOT J);,16,Conditional statements:IF,IF.THEN.ELSE statement Conditional construct:executes a statement block depending on whether or not certain co
13、nditions are satisfied.,Syntax,Exercize,If Expression=TRUE,statement_block is executed Otherwise the conditions in the ELSIF blocks are evaluated Finally,if these are all false,the statements in the ELSE block are executed.,Boolean(AND,OR,NOT,XOR)Comparison(=,=,=).,Features,IF expression THEN statem
14、ent_block;ELSIF expression THEN statement_block;ELSE statement_block;END_IF;,Note expression contains the operators:,Management of a range-550,950 C with NTC probe.,17,Conditional statements:CASE,CASE.OF.statement,Syntax,Conditional construct:selects the statements to be executed depending on the va
15、lue of an integer expression.,CASE expression OF selector_1:statement_block;selector_2,selector_3:statemnt_block;selector_4.selector_5:statemnt_block;selector_6,selector_7.selector_8:statemnt_block;ELSE statemnt_block;END_CASE;,Example,Speed management of a fan.,18,The Function,It can be comparable
16、to a Black box:it works on a Input parameters configuration,and it always produces in Output the same result for the same Inputs.It lets not repeat many times the same code within the project,as instead it is for macroblocks in FBD environment.At each invocation of the function,the same code will be
17、 always executed.,What does a Function do?,It read Inputs,no outputs,but can have a return valueIt executes the code of the functionIt writes the result in a Return ValueA function doesnt have a memory stateIt always produces the same result for the same inputs.,The function Add_3,What does a Functi
18、on contain?,The list of parameters that are passed as inputsProbable Local variables,only for its internal useThe code of the function,What is a Function?,19,FUNCTION statement,The table below lists all properties of a function.,Summary,20,Pass by value(VAR_INPUT),In the pass by value the Actual Par
19、ameters are copied in Formal Parameters.,Actual Parameters,Formal Parameters,Modifications dont have effect on Actual Parameters.,21,Pass by Reference(VAR_IN_OUT),Pass by Reference,Actual Parameters,Formal Parameters,Modification,Sometimes it is necessary to modify the variable value passed to the f
20、unction,and render such modification outside immediately visible.This modality is called Pass by Reference and it is realized using keyword VAR_IN_OUT.In Pass by Reference the Formal Parameter point to the same cell of memory that contains the value of Actual Parameter.,22,Variables scope,23,RETURN
21、statement,Syntax,The RETURN statement is used to exit from a Function,Function Block or the Program before the end.,FUNCTION My_functionlist_statements_1;RETURN;list_statements_2;END_FUNCTION,1st Example,2sd Example,In the case of a Function or Function Block,the statement interrupts execution after
22、 list_statements_1,and passes control to the calling POU without executing list_statements_2.In the case of the Program,the statement closes the Program.,24,ARRAY statement,Syntax,Exercize,Array_name:ARRAYelem_1.elem_n OF Type;where:,Simulation,elem_1 and elem_n are INT numbers or constants(they can
23、not be variables)and represent the limits of the arrayelem_n=elem_1,the difference+1 indicates the number of elements in the arrayType identifies the elementary data type elements inside the array or Structure type,25,Array Breakthrough(exceeded limits),Example,Run-Time error on Simulator,Run-Time e
24、rror on pCO Place 2 integer variables on a Mask related to library functions:The position of error in the Strategy Editor ST:go in simulation and then press insert High part and Low part,When a variable is used to access the elements of an array,care must be paid to ensure the size of the array is n
25、ot exceeded.If run-time the index value exceeds the size of the array,this will entail the re-boot of the pCO.,NoteTo reset error variables use this library functions:,26,Iteration statements:FOR,FOR.DO.Statement,FOR variable:=initial_expression TO final_expression BY increase_expression DO statemen
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