MC-Basic Language Fundamentals
Contents
Refer to
- MC-Basic Commands - a list of all MC-Basic commands
- MC-Basic Constants - a list of keywords that can be used instead of explicit numeric values for parameters that have a discrete range of possible values
- MC-Basic Operators - the different types of operators and their relative precedence
- MC-Basic Programs - projects and tasks
- MC-Basic Libraries - reusable code for subroutines and functions
- MC-Basic Generic Elements - reusable code for setup or query properties
- MC-Basic Points
- MC-Basic C-Interface
- Error Codes
Introduction
The softMC is programmed in MC-Basic, a version of the BASIC programming language enhanced for multitasking motion control. If you are familiar with BASIC, you already know much of MC-Basic.
To develop your application on the softMC, you must install ControlStudio.
Command Reference Format
All MC-Basic commands are presented in the list of MC-Basic Commands. The reference entry for each command contains the information needed for correct use of the command or property. Each entry for a command or property contains all or most of the following elements:
| Description | A description of the command or property. |
| Short Form | Where applicable, a short form of the longer command can be used to simplify typing the command or property name. In such instances, the short form is denoted. The short form of a command or property name may be used interchangeably with the long version. |
| Syntax | In describing the syntax of an instruction, different notations are used. |
| < > | Field to be filled by user. For example, ABS ( <expression> ) indicates that <expression> is the user\’s data. |
| { } | Optional data. Many instructions have optional fields, which are used to override default values. For example, the VelocityCruise property is optional within a Move command. However, there is an exception to this rule, in that \{ \} are used for vector notation. When the optional data may be repeated, an asterisk (\*) is used to indicate this. |
| | | Or. Indicates that either one of the values may be used. |
| Availability | Various versions of the firmware add new features, and often significantly change the syntax or behavior of commands and properties. The attribute Availability included in the descriptions denotes the applicability of each function (command, property)to the specified version of the firmware. |
| Type | Refer to the section Data Types, below. |
| Range | Range of valid values |
| Units | When parameter values imply dimensional units of measurement, these units are specified in the description of the command or property where they apply. |
| Default | Default value |
| Scope | Instructions can be executed from any of three contexts: the configuration file (CONFIG.PRG), the terminal, and within a task. Not all instructions can be executed from all three contexts; their scope of operation is limited. For each instruction, the scope of operation is defined. |
| Limitations | Even when an instruction can be executed in a given context, there may still be limitations on its use. For example, a MOVE command can be executed from within a task, but there is a limitation in that the motion element being moved must first be attached to the task by the ATTACH command. |
| Examples | Examples of use |
| See Also | Links to related commands |
Instructions
Instructions are the building blocks of BASIC. Instructions set variables, call functions, control program flow, and start processes such as events and motion. In this documentation, the terms instruction and command are used interchangeably.
Syntax is the set of rules that must be observed to construct a legal command (that is, a command the softMC can recognize).
MC-Basic is line-oriented. The end of the line indicates the end of the instruction. Whitespace (i.e., spaces and tabs within the statement line and blank lines), is ignored by the BASIC interpreter. You can freely use indentation to delineate block structures in your program code for easier readability. The maximum allowed length of a line is 80 characters.
MC-Basic is case insensitive. Commands, variable names, filenames, and task names may be written using either upper case or lower case letters. The only exception is that when printing strings with the “Print” and “PrintUsing” commands, upper and lower case characters can be specified.
Syntax uses the following notation:[ ]indicates the contents are required{ } indicates the contents are optional for the command
Example lines of text are shown in Courier type font and with a border:
X = 1
Types of Instructions
There are many types of instructions: comments, assignments, memory allocation, flow control, task control, and motion.
Comments allow you to document your program. Indicate a comment with either the Rem command or a single apostrophe ('). You can add comments to the end of an instruction with either Rem or an apostrophe.
Rem This is a comment ' This is a comment too. X = 1 'This comment is added to the line X = 1X = 1 REM This is a comment too
Use comments generously throughout your program. They are an asset when you need support from others and they avoid confusing code.
Declarations allocate softMC memory for variables and system elements (groups, cam tables, etc.). This might be a simple type as an integer, or a complex structure as a cam table.
Assignments Assignment instructions assign a new value to a variable.
The syntax of an assignment is [Lvalue] [=] [expression]
For example:
X = Y + 1
The term, Lvalue, is a shorthand notation, which indicates the value to the left of the equals sign. Valid Lvalues are variables or writable properties, which can be assigned. Expressions can be variables, constants, properties and function calls, as well as various combinations of them in arithmetic and logical statements . An exception to this rule is generic elements’ assignment, at which the right side of the equal sign is not an expression, but an axis or a group (either real or generic), and Lvalue is a generic elements. If you assign a Double (floating point) value (expression, variable or constant) to a Long variable, the fractional portion of the double value is truncated, and the integer portion is assigned to the long variable. To query a variable or expression from the ControlStudio terminal window, use the PRINT or ? command:
PRINT 1/100 ? X1
MC-Basic also provides the standard PRINTUSING (PrintU) command for formatted printing.
Commands for flow control change the way your program is executed. Without flow control, program execution is limited to processing the line immediately following the current command. Examples of flow control include GOTO, FOR…NEXT, and IF…THEN.
MC-Basic is a multitasking language in which many tasks can run concurrently. Generally, tasks run independently of each other. However, tasks can control each other using inter-task control instructions. One task can start, idle, or terminate another task.
Most commands are started and finished immediately. For example:
x = 1 ' this line is executed completely… y = 2 ' …before this line is started
For general programming, one command is usually finished before the next command starts. Effects of these commands do not persist beyond the time required to execute them. However, the effects of many other commands persist long after the execution of the command. In general programming, for example, the effects of opening a file or allocating memory persist indefinitely. In real-time systems, persistence is more complicated because the duration of persistence is less predictable.
Consider a command that specifies a 1,000,000 counts move on an axis named, A2:
Move A2 1000000.0 Y = 2
The softMC does not wait for the 1,000,000 move to be complete before executing Y=2. Instead, the first command starts the motion and then the softMC continues with the next line (Y = 2). The move continues well after the move command has been executed.
Persistence can affect programs. For example, you may not want to start one move until the previous move is complete. In general, you need access to persistent processes if you are to control your program according to their state of execution. As you will see later, MC-Basic provides this access.
Line Concatenations
Performs concatenation of program or command line input. Useful when input string is longer than translator buffer (128 chars).
- Symbol
- \
- Example
A = B + \ C + D
Is equal to:
A = B + C + D
Constants and Variables
All constant, variable and system element names must start with an alphabetical character (a-z, A-Z) and may be followed with up to 31 alphabetical characters, numbers (0-9) and underscores (“_”). Keywords may not be used as names.
Constants
Constants are numbers that are written as ordinary text characters,
Refer to: MC-Basic Constants
Variables
You must declare a variable in MC-Basic before you can it. In the declaration, you define variable name, scope and variable type. MC-Basic supports Long for integer values, Double for floating point values, and String for ASCII character strings.
Besides these basic types, MC-Basic also supports Structure-like variables and some MC-Basic specific types, such as points (Joints and Locations), generic motion elements (Axes and Groups) and UEAs (user error assertions-Errors and Notes).
DeleteVar deletes a global variable. Since variable name can include wildcards, a single DELETEVAR can be used to delete more than one variable.
DeleteVar int1 DeleteVar int* ' Deletes all variables starting with int
Current values of global variables (both scalar and arrays) can be stored in a Prg file, in assignment format, within an automatically executable Program Continue…Terminate Program block. Obligatory parameters of SAVE are the name of storage file, and type of stored variables (could be all types). Optional parameters are robot type (for point variables), variable name (which may include wildcards) and mode of writing to storage file (overwriting or appending). Variable types available for storage through SAVE are longs, doubles, strings, joints and locations, but not structures, user-defined exceptions nor generic motion elements.
Save File = “IntFile.Prg” Type = All VariableName = “int*” ‘ Save all variables starting with int in IntFile.Prg (overwrite file) Save File = “Points.Prg” Type = Joint RobotType = XYZR Mode = Append ‘ Append all joint-type points with XYZR robot-type to Points.Prg file
Scope defines how widely a variable can be accessed. The broadest scope is global. A global variable can be read from any part of the system software. Other scopes are more restrictive, limiting access of variables to certain sections of code. MC-Basic supports three scopes: global, task, and local. Task variables can be read from or written to anywhere within the task where it is defined, but not from outside the task. Local variables can only be used within their declaration block, i.e. program, subroutine or function blocks. The scope of a variable is implicitly defined when a variable is declared using the keywords: Common, Shared, and Dim.
Global variables can be defined within the system configuration task, Config.Prg, within a task files (Prg files), before the program block, within library files (Lib files), before the first subroutine or function block, or from the terminal window of ControlStudio. To declare a variable of global scope use the Common Shared instruction.
Task variables are defined within a task or a library. To declare a variable of task scope use the Dim Shared instruction.
 | NOTE |
| All Dim Shared commands must appear above the Program statement in task files. In library files, all Dim Shared commands must appear above the first block of subroutine or function. The values of variables declared with Dim Shared persist as long as the task is loaded, which is usually the entire time the unit is operational. This is commonly referred to as being static. |
Local variables are defined and used within a program, a subroutine, or a function. To declare a local variable, use the Dim instruction. The Dim command for local variables must be entered immediately below the Program, Sub, or Function statement. Local variables cannot be declared within event blocks, and events cannot use local variables declared within the program.
Data Types
Numeric Data Types
MC-Basic has two numeric data types: Long and Double. Long is the only integer form supported by MC-Basic. Long and Double are MC-Basic primitive data types.
| Type | Description | Range |
| Long | 32 bit signed integer | -2,147,483,648 (MinInteger) to 2,147,483,647 (MaxInteger) |
| Double | Double precision floating point(about 16 places of accuracy) | ±1.79769313486223157 E+308 |
String Data Type
MC-Basic provides the string data type which consists of a string of ASCII-coded characters. MC-Basic strings are dynamic. Reallocation of memory for new strings is preformed through a simple assignment of the string variable, and there is no need to specify the length of the new string. A full complement of string functions is provided to create and modify strings.
| Type | Description | Range |
| String | ASCII character string (no string length limit) | 0 to 255 (ASCII code) |
String parameters are based on the 8-bit ASCII character code set, which comprises 255 character codes, with code values from 1 to 255.
UTF-8
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In UTF-8 supporting versions (4.5.1 and higher), range was expanded to character codes from 0 to 255, since NULL characters are no longer cut out from strings. If string functions are used with parameter values outside the specified range, the behavior of the function may vary (e.g., the function may return an error message, the function may return a value different from the correct value, or the function may return the correct value). String values must be delimited by double quotes (“string value”). The maximum number of characters allowed in a string is limited only by the amount of free memory space.
Point Data Types
Refer to: Points
MC-Basic has two point data types: JOINT and LOCATION. A point variable is related to a robot type. Robot type examples: XY – two axes XY table, XYZ – three axes XYZ system, XYZR – three cartesian axes + roll, etc.
| Type | Description | Range |
| Joint | A set of 2-10 double precision floating point joint (motor) coordinates | ±1.79769313486223157 E+308 for each coordinate |
| Location | A set of 2-10 double precision floating point cartesian coordinates | ±1.79769313486223157 E+308 for each coordinate |
Structures
MC-Basic enables definition of structure-like data types, composed of of long, double, string and point (joint and/or location) scalar and array elements. Array elements can have up to ten dimensions. Name of structure type and composition of elements are defined by the user within configuration file (Config.Prg) and library files.
User Error Assertion
MC-Basic has two UEA (user error assertion) data types (severities): Error and Note. Each UEA is defined with a string-type error message given by the user and a unique exception number, which might be determined either by the user or by the system. The softMC handles UEAs similar to internal exceptions.
| Type | Description | Range |
| Error | An ASCII message string and a unique integer exception number | 20001-20499 for user determined exception number 20500-20999 for system determined exception number |
| Note | An ASCII message string and a unique integer exception number | 20001-20499 for user determined exception number 20500-20999 for system determined exception number |
Generic Element Data Types
Refer to: Generic Elements
MC-Basic provides generic element data types designed to serve as a reference to real axes and groups. Through a simple assignment statement, the generic element gets the element identifier (see below) of a real motion element, thus acquiring all its properties. Afterwards, all activities preformed on the generic element identically affect the real element. The referenced element can be changed, through recurring assignments, as many times as the user wishes.
| Type | Description | Range |
| Generic Axis | An integer element identifier | 0 (before first assignment) 1 to number of axes in system (up to 32) |
| Generic Group | An integer element identifier | 0 (before first assignment) 33 to number of groups in system (up to 64) |
Each real motion element gets a unique element identifier from the system during its declaration. Axes get successive element identifiers ranging from 1 to 32 according to axis number. Groups get successive identifiers ranging from 33 to 64 according to declaration order. Value of element identifier can be queried directly through ELEMENTID.
SYS.NUMBERAXES = 2 Common Shared G2 As Group AxNm = A1 AxNm = A2 Common Shared G1 As Group AxNm = A1 AxNm = A2 ? A1.ELEMENTID 1 ? A2.ELEMENTID 2 ? G2.ELEMENTID 33 ? G1.ELEMENTID 34
MC-Basic uses integers to support Boolean (logical) operations. Logical variables have one of two values: true or false. MC-Basic uses type Long to support logical expressions. The value 0 is equivalent to false. Usually, 1 is equivalent to true, although any non-zero value is taken to be true. Boolean expressions are used in conditional statements such as If…Then, and with Boolean operators like And, Or, and Not.
Arrays can be any data type. Arrays may have from 1 to 10 dimensions. The maximum number of elements in any dimension is 32,767. Array dimensions always start at 1.
Structures
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A structure is a new data type used for storing a list of variables of different type in one variable.
Definition
Since a structure is a user-defined data type; it must first be defined. Structure type definition can be done only in the Config.prg file (before the PROGRAM block, at the declaration level), using the following syntax:
TYPE <structure_type_name>
<element_name>{[]} AS <element_type> {OF <robot_type>}
…
END TYPE
This block defines the name of the structure type and the names, types and array sizes of the various structure elements (fields). Data types supported as structure elements are: long, double, string, and points (JOINT and LOCATION). Array elements can only have a single dimension. The maximum structure block can include: 100 longs, 100 doubles, 100 strings, 100 points JOINTs and/or LOCATIONs), 10 long-type arrays, 10 double-type arrays, 4 string-type arrays and 2 point-type arrays JOINTs and/or LOCATIONs). The total size of the MC-Basic structure is limited. The maximum number of each type of element is fixed. Trying to define more structure elements than allowed results in a translation error. An array of structures may have up to 10 dimensions.
Declare
You must declare a structure before you can use it. If you want to declare a structure variable, you must first declare a structure data type and then use this data type structure to declare the variable. The structure data type definition can be done in the Config.prg file only with the following syntax (before the PROGRAM token, at the declaration level):
TYPE <variable_name>
<variable_name> as <type>
<variable_name> as <type> {<of> <robot_type>}
…
END TYPE
This block defines the new element names of the structure type. The different types supported for the structure are: long, double, string, and points. The maximum structure block is defined as:
100 longs
100 doubles
100 strings
100 points
Syntax
(COMMON SHARED|DIM {SHARED}) <variable_name> AS <variable_name>
or
(COMMON SHARED|DIM {SHARED}) <variable_name>[<index>] AS <variable_name>(arrays of structure)
where the second variable name = the structure type
For example:
In config file -> Type X Type as Long Length as Long End Type In application file -> Dim shared s1 as X Program ?s1->Type End program
Do not define the size of the structure data type. The size of the structure is constant. If you declare more structure elements than allowed, a translation error is generated.
Assignment
The assignment of a structure uses the following syntax:
<variable_name> = <expression> where <expression> is of structure type
Whole structure assignment is allowed only if both structures are of the same structure type. For example:
Dim STa1 As Type_1 Dim STb1 As Type_1 Dim STa2 As Type_2 STa1 = STb1 -> Structure types match STa2 = STa1 -> Error - structure type mismatch
Elements
A structure element is addressed through the structure’s name and the arrow sign. For example:
<structure_name>{[]…}-><element_name>{[]}
Structure elements are handled almost like regular variables. Structure elements are printed, assigned, participate in mathematical operations, and string-type elements are concatenated to other strings. They can also serve as arguments of system functions (SIN, UCASE$, etc.), used in logic statements and as conditions of flow control statements and event definitions. For example:
Common Shared ST As STRUCT PRINT ST->LongElm1 ST->LongElm2 = 21.2 * ST->LongArrElm[1] ? UCASE$(“String Element Is: “ + ST->StringElm) IF ST->LongElm1 > 0 THEN SELECT CASE ST->LongElm2
System Elements
There are several system elements: axes, groups, cam tables, PLSs, conveyers and compensation tables. These are not regular data types, but are more like user interfaces of the system's internal memory or internal function calls. You cannot handle them as a whole in expressions. Each system element has a set of properties, which is accessed through syntax resembling data elements of a structure, using the point character.
Despite the syntax, properties are not data elements, since a system element and its properties are not located on a continuous block of memory. All properties return a value, so they can be printed, combined in expressions and passed by value to functions and subroutines. Many properties are also writable and can be assigned like variables.
Unlike variables, properties do not have a fixed address in memory and cannot be passed by reference. Data types of properties are Long, Double, String, Joint and Location. For axis A1 and cam table Cam1, and a long type variable named Var1:
? A1.Enable ‘ Query A1.Enable = 1 ‘ Set (read-write property) ? A1.PositionCommand ‘ Query A1.PositionCommand = 0 ‘ Syntax Error (read-only property) Var1 = Cam1.Cycle ‘ Query Cam1.Cycle = -1 ‘ Set (read-write property) Var1 = Cam1.Inuse ‘ Query Cam1.Inuse = 1 ‘ Syntax Error (read-only property)
Units
Many variables have associated units. This include variables, which contain quantities of position, velocity, acceleration, and time. Some units are fixed. For example, time is always in milliseconds. MC-Basic allows you to define units of position, velocity and acceleration independently. In the next chapter, we will discuss how to set up units.
Expressions
Refer to: MC-Basic Operators
Expressions are combinations of operators and value-returning entities, such as variables, constants, function calls, which are all calculated into a value. In MC-Basic, expressions can also contain unique entities like element properties (see above) and system properties (see below). Operators (like + and -) specify how to combine the variables and constants. Expressions are used in almost all commands.
An expression has one of two syntax forms
[operand] [binary operator] [operand][unary operator] [operand]
An operand can be a constant (123.4), variable name (X), or another expression. Most operators are binary (they take two operands), but some are unary (taking only one operand). So, -5.5 is a valid expression. It has the unary minus (also called negation) and a single operand.
There are two types of expressions: algebraic and logical (or Boolean).
Algebraic expressions are combinations of data and algebraic operators. The results of all algebraic operations are converted to double precision floating-point after executing the expression.
Logical expressions are combinations of data and logical operators. For example, X1 And X2 is a logical expression. The data and results of logical elements are type Long. Double variables are not allowed in logical expressions. The terms, logical and Boolean are considered interchangeable.
Logical expressions are evaluated from left to right. They are evaluated only far enough to determine the result. So, in A And B And C, if A is 0 (false), the result is false without evaluating B or C.
Precedence dictates which operator is executed first. If two operators appear in an expression, the operator with higher precedence is executed first. For example, multiplication has a higher precedence than addition. The expression 1+2*3 is evaluated as 7 ((2 * 3) + 1), not 9 ((2 + 1) * 3). The minus sign in the math operators’ table (below) is sometimes confusing since it shows up twice in the table: once with a high precedence (unary negation) and once with low precedence subtraction (binary minus). This difference in precedence is intuitive: 5 * -6 only makes sense if the negation is executed first.
The tables that follow list different types of operators. The entries in the tables are listed in order of precedence: the higher in the table, the higher the operator precedence. Also, the tables themselves are arranged in order of precedence with respect to one another. Math operators have the highest precedence. So, all math operations are executed before any other type of operator is executed. Finally, any time you need to change the standard precedence, use parentheses. Parentheses have the highest precedence of all.
| Algebraic Operator | Symbol | Unary/Binary | Operand Type |
| Parentheses | ( ) | NA | double, long, string, joint, location |
| Exponentiation | ^ | Binary | double, long |
| Negation | - | Unary | double, long, joint, location |
| Unary Plus | + | Unary | double, long, joint, location |
| Multiplication | * | Binary | double, long, joint, location |
| Division | / | Binary | double, long, joint, location |
| Modulo | Mod | Binary | double, long |
| Addition | + | Binary | double, long, string, joint, location |
| Subtraction | - | Binary | double, long, joint, location |
| Compound | : | Binary | location |
| Relational Operator | Symbol | Binary/Unary | Operand Type |
| Parentheses | ( ) | Not applicable | double, long, string |
| Equality | = | Binary | double, long, string |
| Inequality | <> | Binary | double, long, string |
| Less than | < | Binary | double, long, string |
| Greater than | > | Binary | double, long, string |
| Less than or equal to | <= | Binary | double, long, string |
| Greater than or equal to | >= | Binary | double, long, string |
| Word-wise Logical Operator | Symbol | Binary/Unary | Operand Type |
| And | And | Binary | long |
| Or | Or | Binary | long |
| Exclusive or | Xor | Binary | long |
| Not | Not | Unary | long |
| Bit-Wise Logical Operator | Symbol | Binary/Unary | Operand Type |
| Bitwise Negation | BNot | Unary | long |
| Bitwise And | BAnd | Binary | long |
| Bitwise Or | BOr | Binary | long |
| Bitwise Xor | BXor | Binary | long |
| Shift Left | SHL | Binary | long |
| Shift Right | SHR | Binary | long |
Negation is simply placing a minus sign in front of a constant or variable to invert its arithmetic sign. Modulo division produces the remainder of an addition. For example, 82 Mod 5 is equal to 2 (the remainder of 82/5). If the first operand is negative, the resultant value is negative (-2). The sign of the result is determined by the sign of the first operand, and the sign of the second operand has no effect.
The relative precedence of exponentiation and negation may seem somewhat counter-intuitive. The following examples illustrate the actual behavior.
Common shared D as double D = -1 ? D^2 1 ? -1^2 -1
In the second section of the above example, exponentiation is performed first then negation is performed.
Common shared D as double D = -1 ? D = -1 1
In the example above, the “=” sign is taken as a relational operator (i.e., Is D = -1?) The relation is True, or 1.
? D^2 = -1^2 0
In the example above, the “=” sign is taken as a relational operator, (i.e., Is D^2 = -1^2?). Again, the exponentiation is performed first, and then the relation is evaluated as False, or 0.
The "+" operator, when used with strings, performs concatenation of strings.
In points, “+” (addition) and “-“ (subtraction) operators can be used between points of the same type and size, or between a point and a long or double type scalar. On the other hand, “*” (multiplication) and “/” (division) operators can only be operated between a point and double or long scalar, but not between two points.
In Logical operations, every value that is not 0 is assumed true and set to 1. And-ing combines two values so the result is true (1) if both values are true (that is, non-zero). Or-ing combines them so the result is true (1) if either value is true. Exclusive-Or produces true if one or the other value is true. It produces false (0) if both or neither are true. Before logical operations begin, all operands are converted to 1 (true) or 0 (false). The rule is that everything that is not 0 becomes 1.
Bit-wise expressions differ from logical expressions in that there may be many results from a single operation. Bitwise operations are frequently used to mask I/O bits. For example, the standard softMC inputs can be operated on with BAnd (Bitwise And) to mask off some of the inputs. The following example masks off all bits of the digital outputs, except the rightmost four:
Dim Shared MaskedBits As Long MaskedBits = System.Dout Band 0xF ‘Mask all but rightmost four bits
All bitwise operations produce 32-bit result from two 32-bit numbers. Bitwise operations are really 32 independent, bit-by-bit operations. For example:
15 (Binary 1111) BAnd 5 (Binary 101) is 5 (Binary 101)BNot 15 is 0xFFFFFFF0.
Automatic Conversion of Data Types
If the assignment of an expression is an integer, the expression is still evaluated in double precision. For example:
Common Shared I as Long I = 6.33 * 2.79
The value of the expression (6.33 * 2.79) is converted from double to long when the value (17) is copied into I. In the conversion to long, the number is truncated to the integer portion of the floating-point value.
Math Functions
MC-Basic provides a large assortment of mathematical functions. All take either numeric type as input (Double and Long) and all but Int and Sgn produce Double results. Int and Sgn produce Long results.
| Abs(x) | Returns the absolute value of X. |
| Acos(x) | Returns the arc cosine of X. X is assumed to be in radians. |
| Asin(x) | Returns the arc sine of X. X is assumed to be in radians. |
| Atan2(Y, X) | Returns the inverse tangent of Y/X in radians. The range of the result is between ±PI radians (±180°). Atan2 is an improvement over ATN(Y/X) in that it works correctly if X is zero, and if X<0. |
| Atn(X) | Returns the inverse tangent of X in radians. The range of the result is between ±PI/2 radians (±90°). |
| Cos(X) | Returns the cosine of X. X is assumed to be in radians. |
| Exp(X) | Returns ex. |
| Int(X) | Returns the largest long value less than or equal to a numeric expression (for example, ?Int(12.5) returns 12 ?Int(-12.5) returns -13) |
| Log(X) | Returns the natural logarithm of X. X must be > 0. If you want the base-10 log, use Y = LOG(X)/LOG(10). |
| Sgn(X) | Returns the arithmetic sign of X. If X > 0, return 1. If X < 0, return -1. If X = 0, return 0. |
| Sin(X) | Returns the sine of X. X is assumed to be in radians. |
| Sqrt(X) | Returns the positive square root of X. X must be >= 0. |
| Tan(X) | Returns the tangent of X. X is assumed to be in radians. |
| Round(X) | Returns the integer nearest to X. If X falls exactly between two integers (for example, 1.5), return the even integer. So 1.5 and 2.5 round to 2. |
String Functions
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MC-Basic supports all the common string functions supported in standard BASIC.
| ASC(S,I) | Returns an ASCII character value from within a string, S, at position, I. |
| BIN$(X) | Returns the string representation of a number (X) in binary format (without the Ob prefix). |
| CHR$(X) | Returns a one-character string corresponding to a given ASCII value, X. |
| HEX$(X) | Returns the string representation of a number (X) in hexadecimal format (without the 0x prefix). |
| INSTR(I,SS,S) | Returns the position, I, of the starting character of a substring, SS, in a string, S. |
| LCASE$(S) | Returns a copy of the string, S, passed to it with all the uppercase letters converted to lowercase. |
| LEFT$(S,X) | Returns the specified number, X, of characters from the left-hand side of the string, S. |
| LEN(S) | Returns the length of the string, S. |
| LTRIM$(S) | Returns the right-hand part of a string, S, after removing any blank spaces at the beginning. |
| MID$(S,I,X) | Returns the specified number of characters, X, from the string, S, starting at the character at position, I. |
| RIGHT$(S,X) | Returns the specified number of characters, X, from the right-hand side of the string, S. |
| RTRIM$(S) | Returns the left-hand part of a string, S, after removing any blank spaces at the end. |
| SPACE$(X) | Generates a string consisting of the specified number, X, of blank spaces. |
| STR$(X) | Returns the string representation of a number, X. |
| STRING$(X,\{S\},\{Y\}) | Creates a new string with the specified number, X, of characters, each character of which is the first character of the specified string argument, S, or the specified ASCII code, Y. |
| UCASE$(S) | Returns a copy of the string, S, passed to it with all the lowercase letters converted to uppercase. |
| VAL(S) | Returns the real value represented by the characters in the input string, S. |
In UTF-8 (supported in firmware version 4.5.1 and later), NULL characters are not cut from strings. The string resulting from concatenation is composed from 'A\0B'; i.e., there is a NULL character in the MIDDLE of the string:
Display cuts the string in the middle NULL:
-->?"A" + Chr$(0) + "B"
A
Mid$ gives NULL for the second character:
-->?Mid$("A" + Chr$(0) + "B", 2, 1)
-->
Value of Len is 3:
-->?Len("A" + Chr$(0) + "B")
3.000000000000000e+00
Len of Chr$(0) is 1:
-->?Len(Chr$(0))
1.000000000000000e+00
In firmware versions prior to 4.5.1 (UTF-8 not supported), NULL characters could not appear in the middle of strings, since the concatenation process cut these characters from the resulting string.
System Commands
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NURIT: UPDATE THIS LIST. ADD MISSING COMMANDS.
DELETE ALL COMMANDS THAT ARE NO LONGER SUPPORTED. YOU CAN HIDE IF YOU DO NOT WANT TO DELETE
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System commands provide information about the system. You can issue these commands at any time either from task, terminal or the CONFIG.PRG file (with some exceptions).
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| AxisList | Returns a comma-separated-list of the axes\’ names defined in the system. If wildcards are used, the query returns the proper axes. |
| BreakPointList | Lists all the breakpoints in the task, loaded to memory. |
| CamList | This query returns a list of the cam table names defined in the system. If wildcards are used, the query returns the proper existing cam names. |
| Dir | Lists all files that exist on the RAM disk and on the Flash disk. The File Specification may contain the \* and ? wildcard characters, in order to refine the list. When invoked without a parameter, all the files are listed. |
| ErrorHistory | Displays the log file containing the last 64 errors that occurred in the system. |
| ErrorHistoryClear | Clears the error log file. |
| EventList | Lists the names of the existing events and their states. If a task name precedes EventList, only events belonging to the specified task are listed. |
| GroupList | Lists the names of the groups defined in the system. Each group name is followed by a list of the axes\’ names that are part of that group. |
| PlsList | Returns a list of the PLS names defined in the system. If wildcards are used, the query returns the correct existing PLS data. |
| ProgramPassword | Sets the file password and toggles the password protection state. |
| Tasks | Reset All removes all tasks, variables, and system variables from program memory. All external outputs are turned off and all drives are disabled. Reset All runs Config.prg, not Autoexec.prg. Reset All is only issued from the terminal. Reset Tasks removes all tasks from memory, but leaves system variables loaded. It deallocates all defined variables and user programs. Reset Tasks does not disable motors, or reset outputs. Reset Tasks is only issued from the terminal. |
| System.AccelerationRate | Queries or sets the system acceleration exchange rate. |
| System.AutostartTask | Queries or sets the name of the auto-start task. The default auto-start task is Autoexec.Prg. Assignment of an empty string prevents auto-start task run. |
| System.AverageLoad | Returns the average realtime load on the CPU. This is the average realtime load measured during a 0.5 second interval. |
| System.Clock | Returns the number of system clock ticks. This is the clock run by the operating system. One clock tick corresponds to 1 millisecond. |
| System.CpuType | Returns the type and model of the CPU that was found during the system\’s power-up. Supports only Intel, AMD and Cyrix processors. |
| System.Date | Queries or sets the date. The date is entered as a character string and must be enclosed between double quotes (“). The parameters Day, Month, and Year, must be separated with the / (slash) character. |
| System.DecelerationRate | Queries or sets the system deceleration exchange rate. |
| System.DIn | Returns the value of one or more of the 23 digital inputs. System.DIn returns the values of the individual bits in the system input word. In order to read the value of a single input bit, bit number should be specified as System.DIn.<bit number>. |
| System.DipSwitch | Returns the value of one or more of the eight DIPswitch inputs. System.DipSwitch returns the values of the eight individual bits in the DIPswitch byte. In order to read the value of a single input bit, bit number should be specified as System.DipSwitch.<bit number>. |
| System.DiskFreeSpace | Returns the amount of free space on the flash disk. |
| System.DoubleFormat | Queries and sets the printing format of Doubles. Zero value stands for d.ddddddddddddddde+/-dd style, with precision of 15 digits after the decimal point. 1 relates to the ddd.ddd style if the exponent is between -4 and 5, and to d.de+/-dd style otherwise. Setting can be done only in Config.Prg file, and therefore requires system reset (through RESET All or hardware reset). |
| System.DOut | Queries and sets the value of one or more of the 20 digital outputs. System.DOut sets or returns the values of the individual bits in the system output word. In order to read or write into a single output bit, bit number should be specified as System.DOut.<bit number>. |
| System.Enable | Enables and disables the system. |
| System.Error | Queries the last system error message. |
| System.ErrorHandlerMode | Determines the scope of the effect of an error occurring in task context. When the value ofSystem.ErrorHandlerMode is one (the default value), the error will affect the entire system by stopping all motion, idling all tasks that have attached elements and turning off System.Motion flag. Setting this property to zero results in limiting the Motion stop and task idling to the erroneous task itself. |
| System.ErrorNumber | Queries the number of the last system error and returns only the error number. |
| System.ErrorPrintLevel | Controls which errors are printed, according to the severity of the error. Only asynchronous errors are printed. Synchronous errors are not affected. |
| System.Information | Returns information found during system power-up. Performs a test on the SERCON chip cycle time. The result is the average cycle time found in a 500 ms test. |
| System.IPAddressMask | Queries or sets the IP address and subnet mask for the Ethernet interface. |
| System.JerkRate | Queries or sets the system jerk exchange rate. |
| System.Led | Queries and sets one or more of the three general purpose LEDs. In order to read or write into a single LED, LED number should be specified as System.LED.<LED number>. |
| System.MaxMemBlock | Returns the size (in bytes), of the largest block of free memory. |
| System.MCDouble | Reads or writes to one of eight double-type DPRAM variables available for use by the softMC. |
| System.MCInteger | Reads or writes to one of the long-type DPRAM variables available for use by the softMC. |
| System.Motion | Enables and disables Motion commands. |
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| AxisList | Returns a comma-separated-list of the axes' names defined in the system. If wildcards are used, the query returns the proper axes. |
| BreakPointList | Lists all the breakpoints in the task, loaded to memory. |
| CamList | This query returns a list of the cam table names defined in the system. If wildcards are used, the query returns the proper existing cam names. |
| Dir | Lists all files that exist on the RAM disk and on the Flash disk. The File Specification may contain the * and ? wildcard characters, in order to refine the list. When invoked without a parameter, all the files are listed. |
| ErrorHistory | Displays the log file containing the last 64 errors that occurred in the system. |
| ErrorHistoryClear | Clears the error log file. |
| EventList | Lists the names of the existing events and their states. If a task name precedes EventList, only events belonging to the specified task are listed. |
| GroupList | Lists the names of the groups defined in the system. Each group name is followed by a list of the axes' names that are part of that group. |
| PlsList | Returns a list of the PLS names defined in the system. If wildcards are used, the query returns the correct existing PLS data. |
| ProgramPassword | Sets the file password and toggles the password protection state. |
| Reset All | Tasks | Reset All removes all tasks, variables, and system variables from program memory. All external outputs are turned off and all drives are disabled. Reset All runs Config.prg, not Autoexec.prg. Reset All is only issued from the terminal.
Reset Tasks removes all tasks from memory, but leaves system variables loaded. It deallocates all defined variables and user programs. Reset Tasks does not disable motors, or reset outputs. Reset Tasks is only issued from the terminal. |
| System.AccelerationRate | Queries or sets the system acceleration exchange rate. |
| System.AutostartTask | Queries or sets the name of the auto-start task. The default auto-start task is Autoexec.Prg. Assignment of an empty string prevents auto-start task run. |
| System.AverageLoad | Returns the average realtime load on the CPU. This is the average realtime load measured during a 0.5 second interval. |
| System.Clock | Returns the number of system clock ticks. This is the clock run by the operating system. One clock tick corresponds to 1 millisecond. |
| System.CpuType | Returns the type and model of the CPU that was found during the system’s power-up. Supports only Intel, AMD and Cyrix processors. |
| System.Date | Queries or sets the date. The date is entered as a character string and must be enclosed between double quotes ("). The parameters Day, Month, and Year, must be separated with the / (slash) character. |
| System.DecelerationRate | Queries or sets the system deceleration exchange rate. |
| System.DIn | Returns the value of one or more of the 23 digital inputs. System.DIn returns the values of the individual bits in the system input word. In order to read the value of a single input bit, bit number should be specified as System.DIn.<bit number>. |
| System.DipSwitch | Returns the value of one or more of the eight DIPswitch inputs. System.DipSwitch returns the values of the eight individual bits in the DIPswitch byte. In order to read the value of a single input bit, bit number should be specified as System.DipSwitch.<bit number>. |
| System.DiskFreeSpace | Returns the amount of free space on the flash disk. |
| System.DoubleFormat | Queries and sets the printing format of Doubles. Zero value stands for d.ddddddddddddddde+/-dd style, with precision of 15 digits after the decimal point. 1 relates to the ddd.ddd style if the exponent is between -4 and 5, and to d.de+/-dd style otherwise. Setting can be done only in Config.Prg file, and therefore requires system reset (through RESET All or hardware reset). |
| System.DOut | Queries and sets the value of one or more of the 20 digital outputs. System.DOut sets or returns the values of the individual bits in the system output word. In order to read or write into a single output bit, bit number should be specified as System.DOut.<bit number>. |
| System.Enable | Enables and disables the system. |
| System.Error | Queries the last system error message. |
| System.ErrorHandlerMode | Determines the scope of the effect of an error occurring in task context. When the value of System.ErrorHandlerMode is one (the default value), the error will affect the entire system by stopping all motion, idling all tasks that have attached elements and turning off System.Motion flag. Setting this property to zero results in limiting the Motion stop and task idling to the erroneous task itself. |
| System.ErrorNumber | Queries the number of the last system error and returns only the error number. |
| System.ErrorPrintLevel | Controls which errors are printed, according to the severity of the error. Only asynchronous errors are printed. Synchronous errors are not affected. |
| System.FlashDiskSize | Returns the size of the Flash disk. |
| System.Information | Returns information found during system power-up. Performs a test on the SERCON chip cycle time. The result is the average cycle time found in a 500 ms test. |
| System.IPAddressMask | Queries or sets the IP address and subnet mask for the Ethernet interface. |
| System.JerkRate | Queries or sets the system jerk exchange rate. |
| System.Led | Queries and sets one or more of the three general purpose LEDs. In order to read or write into a single LED, LED number should be specified as System.LED.<LED number>. |
| System.MaxMemBlock | Returns the size (in bytes), of the largest block of free memory. |
| System.MCDouble | Reads or writes to one of eight double-type DPRAM variables available for use by the softMC. |
| System.MCInteger | Reads or writes to one of the long-type DPRAM variables available for use by the softMC. |
| System.Motion | Enables and disables Motion commands. |
| System.MotionAssistance | Enables and disables display of additional notes returned from the motion task. |
| System.Name | Queries and sets the name of the controller. |
| System.NoMotion | Enables and disables the System.Motion monitoring apparatus. |
| System.NumberAxes | Returns the number of axes currently loaded in the system. This is a read-only variable. It can be used in the terminal window or in any task. |
| System.PeakLoad | Returns the peak realtime load on the CPU. This is the maximum value of the realtime load measured during a 0.5 second interval. |
| System.PipeMode | Queries and sets the type of motion pipe mode. Available types are: active, position only, or position and velocity. |
| System.PrintMode | Queries and sets the printing format of Longs. Optional formats are DECIMAL (decimal format), HEX (hexadecimal format) and BIN (binary format). Default format is decimal. |
| System.RamDriveFreeSpace | Returns the amount of free space on the RAM drive. |
| System.RamSize | Returns the size of the RAM found during the system power-up. |
| System.RtsTimeout | Queries and sets the timeout of the real-time scheduler. |
| System.SerconVersion | Returns the version number of the SERCON chip. |
| System.SerialNumber | Returns the serial number of the softMC. |
| System.ServicePrintLevel | Controls (query or set) printing of service messages (ON or OFF). |
| System.Time | Queries or sets the current time of day. Hours, minutes, and seconds are each specified using two digits. The softMC uses 24-hour clock notation. Time is entered as a character string and must be enclosed between double quotes ("). The parameters, Hours, Minutes, and Seconds, must be separated with : (colon) characters. |
| System.UserAuthorizationCode | Returns the user authorization code. |
| System.VelocityOverride | Queries or sets the system velocity override. |
| System.VelocityRate | Queries or sets the system velocity exchange rate. |
| System.VIn | Returns the value of one or more of the 32 virtual inputs. System.VIn returns the values of the individual bits in the system input word. In order to read the value of a single input bit, bit number should be specified as System.VIn.<bit number>. |
| System.VOut | Queries and sets the value of one or more of the 32 virtual outputs. System.VOut sets or returns the values of the individual bits in the system output word. In order to read or write into a single output bit, bit number should be specified as System.VOut.<bit number>. |
| System.WatchDogTest | Checks the correct operation and timeout of the WatchDog. After the test has finished, the softMC must be rebooted. The test returns either the WD timeout (in ms) when executed successfully, or an error in case of a test failure. |
| TaskList | Lists the names and states of loaded tasks. |
| VarList | Returns a list of the variable names defined in the system. |
| Version | Returns information pertaining to the version of ControlStudio loaded into your softMC. |
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fIX
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| With…End With | Simplifies blocks of code, which set a number of parameters on the same motion element (axis or group). After a With is encountered, all parameters where the element is not specified are assumed to belong to the element specified in the With. With is valid in Configuration, Task, or Terminal contexts. The scope of a configuration With is global, whereas the scopes of both terminal and task With’s are limited to terminal and task, respectively.
To put off the With’s effect, use End With. A task With must be followed by the End With, thus creating a closed With block. A With block must be closed within the same block it was opened (i.e., Program, Sub and Function blocks). For example: A1.VMax = 5000 A1.Vord = 5000 A1.VCruise = 3000 A1.PEMax = 10 A1.PESettle = 0.01 Move A1 100 Can be simplified using With: With A1 VMax = 5000 Vord = 5000 VCruise = 3000 PEMax = 10 PESettle = 0.01 Move 100 End With |
Printing
MC-Basic provides unformatted and formatted printing using the PRINT and PRINTUSING commands.
The Print command (short form, ?) is used to print expressions from the terminal window or from your program. If you issue print commands from the terminal window, they print to the terminal window. If you issue them from your program, they print to the ControlStudio Message Log. You can view the message log by selecting Window, Message Log.
Within programs, PRINT allows you to suppress the carriage return at the end of a line by terminating the command with a comma or a semicolon. Semicolon and comma have no effect when added to the end of print commands from the terminal window.
Print “Hello, “; Print “ world.” 'Prints: Hello, world.
When commas are added to print command as separators between expressions, a tabular space is placed between the expressions in the printed outcome.
Print “Hello, “, Print “ world.” 'Prints: Hello, world.
On the other hand, expressions separated by a semicolon or a space in the print command are printed adjacently.
Print 1,2 1 2 Print 1;2 12 Print 1 2 12
PrintUsing introduces formatting for printing. You can control the format and the number of digits that print. For example, by using the “#” sign and the decimal point, you can specify a minimum number of characters to be printed.
PrintU "The number is #, # ";j1,j2 -->The number is 1, 2
Be aware that using a single format to print more than one expression will result in repetition of any text written within string format according to the number of printed expressions.
PrintU "The number is #, ";j1,j2 -->The number is 1, The number is 2,
By specifying the number of digits to print, data can be printed in tabular form since the number of places printed will not vary with the value of the number.
PrintU “Keep numbers to a fixed length with PrintUsing: ######” ; 100
Be aware that if the number requires more digits than you have allocated, it overruns the space.
PrintU “Overrun: ##” ; 1000000
Takes 7 spaces for 1,000,000 even though PrintU allocates only 2.
For printing of double type expressions, formatted printing also enables to control precision, i.e. number of digits printed after the decimal point.
PrintU “Print PI with 3 digits after decimal point: #.###” ; 3.14159
Prints only 3 digits after the decimal point, while rounding the PI’s value to 3.142.
You can also precede the “#” signs with a “+” to force PrintU to output a sign character (+ or -). Normally, the sign is printed for negative numbers, not positive numbers.
Finally, you can terminate the format string with “^^^^” to force the number to print in exponential format.
PrintU “Exponential format: ####.##^^^^” ; 100
Prints 1e+02. You must include exactly four “^” characters for this format to work.
Be aware that while PRINT and PRINTUSING allow you to print out many expressions on a single line, these expressions are not synchronized to each other. The values can and usually do come from different servo cycles. If you are monitoring motion and need the command to be synchronized, you must use Record.
Normally, printing of longs is done in decimal format. To change printing to Hexadecimal format, type:
System.PrintMode = HEX
To change printing to Binary format, type:
System.PrintMode = BIN
To restore printing to Decimal format, enter:
System.PrintMode = DECIMAL
Printing double floating point numbers is not affected by System.PrintMode. As an alternative to PrintMode, you can place the keywords Decimal, Hex or Binat the end of Print or PrintUsing to print expressions in these formats. Subsequent print instructions (?, PRINT, PRINTU, and PRINTUSING) are not affected.
INPB, INPW, PEEKB, and PEEKW return long values. If you query any of these functions while in PrintMode decimal, the result is misleading. Change to Hex or Bin for the correct result.
System.DoubleFormat , defined from the configuration file , sets the double number printing format for print of double-type numbers.
System.DoubleFormat = 1 – print in Floating point format ( 132.555 )
System.DoubleFormat = 0 - print in Exponential format ( 1.325550000000000e+02 )
Program Sys.DoubleFormat = 1 End Program -->?Sys.DoubleFormat -->1
Output Redirection
Typically, tasks inherit their standard output from the loading context, such as the entry station or standard output of a loader task. Sometimes, you must redirect task output (print) to a different place, such as another entry station or even a virtual entry station. RedirectStdOut/RedirectStdOut$ provides this capability.
-->RedirectStdOut task32.prg NewStdOut=1
NewStdOut may be:
- 1 – Ethernet
- 3 – Virtual Entry Station
- 4 – Ethernet2
Flow Control
Flow control is the group of instructions that control the sequence of execution of all other instructions. For detailed information on any of the flow control commands (including examples), refer to the MC Reference Manual.
If…Then is the most basic flow control statement. The syntax of If…Then is:
If condition Then
<first statement to execute if condition is true>
{multiple statements to execute if condition is true}
{Else
<first statement to execute if condition is false>
{multiple statements to execute if condition is false}}
End If
where:
If…Then must be followed by at least one statement.
Else is optional, but if present must be followed by at least one statement.
There is no Else if. If you use an If after an Else, you must place the If on a new line.
Select…Case is an extension of If…Then. Anything that can be done with Select…Case can also be done with If…Then. Many times, Select…Case simplifies programming logic.
On the first line of a Case block of commands, you specify the variable or expression you want tested. For example:
Select Case I
Tests the variable I for a range of conditions.
You can also select expressions:
Select Case I - M/N
After you have specified the variable or expression, list one or more values or value ranges that the variable can take. There are four ways you can specify cases:
- Exact Value
- Logical Condition
- Range
- Else
The syntax of Select…Case is:
Select Case SelectExpression
{Case Expression1
{statements to be executed if SelectExpression = Expression1}}
{Case Expression2 {statements to be executed if SelectExpression = Expression2}}
{Case Is RelationalOperator Expression3 {statements to be executed if the condition is true}}
{Case Expression4 To Expression5 {statements to be executed if SelectExpression is between values}}
{Case Else {statements to be executed if none of the above conditions are met}}
End Select
where
SelectExpression is a Long, Double or String expression
in Case…To…, if Expression4 > Expression5, the case is never true; no error is flagged.
Select…Case block. The following example puts all four types of cases together:
Program Dim N as Long Select Case N Case 0 Print "N = 0" Case 1 Print "N = 1" Case is >=10 Print "N >= 10" Case is < 0 ‘No requirement for statements after Case Case 5 TO 9 Print "N is between 5 and 9" Case Else Print "N is 2, 3, or 4" End Select End Program
For…Next statements allow you to define loops in your program. The syntax is:
For counter = Start To End {Step Size}]
{Loop Statements}
Next {counter}
where
If Size is not defined, it defaults to 1.
The loop is complete when the counter value exceeds End. For positive Size, this occurs when counter>End. For negative Size, when counter<End.
Counter, Start, End, and Size may be Long or Double.
For example:
For I = 2 TO 5 Print "I = " I 'Prints 2, 3, 4, 5 Next I For I = 4 TO 2 STEP –0.5 Print "I = " I 'Prints 4.0, 3.5, 3.0, 2.5, 2.0 Next
While…End While allows looping dependent on a dynamic condition. For example, you may want to remain in a loop until the velocity exceeds a certain value.
The syntax of While is:
While Condition
{statements to execute as long as condition is true}
End While
where
The condition is evaluated before any statements are executed. If the condition is initially false, no statements are executed.
Statements are optional. If none are included, While…End While acts as a delay.
You can have any number of statements (including zero) to be executed.
For example:
Program While A2.VelocityFeedback < 1000 Print "Axis 2 Velocity Feedback still under 1000" End While End Program
Using the While or Do…Loop, the CPU repeatedly executes the While block (even if the block is empty). This is sometimes a problem. These commands do not relinquish system resources to other tasks. If you want to free up CPU resources during a While block or Do…Loop, include the Sleep command within the block as follows:
Program While A1.VCmd < 1000 Sleep 1 End While End Program
The Do...Loop is similar to While except that the statement block is executed before the first evaluation of the condition. With the Do...Loop, the statement block are always executed at least once. Do...Loop also allows an option on the condition. Use While to execute while the condition is true, or Until to execute while the condition is false. The syntax of the Do...Loop is:
Do
{statements}
LOOP While|Until Condition
where:
The statements are executed at least once.
Statements are optional. If none are included, Do...Loop acts as a delay.
For example:
Dim Shared i as Long Program i = 0 Do i = i + 1 Print i Loop Until i = 10 End Program
or, equivalently, you can use Loop While:
Dim Shared i as Long Program i = 0 Do i = i + 1 Print i Loop While i < 10 End Program
GoTo unconditionally redirects program execution. The syntax is:
GoTo Label1
…
Label1:
where:
Label1 is a valid label within the same task as the GoTo.
The label must be on a separate line.
You can only branch within a Program, Event, Function, or Subroutine.
You can GoTo a label placed within a program block (If…Then, For…Next, Select…Case, While…End While, and Do...Loop) only if the GoTo and label are within the same block.
If the program is within a program block, you cannot GoTo a label outside that block.
Avoid GoTo wherever possible. History has shown that excessive use of GoTo makes programs harder to understand and debug. Use the other program control statements whenever possible.
Error Trapping
There are four ways to specify catch statements: Exact Value, Logical Condition, Range, and Else. The syntax used is:
Catch Error_Number {statements to execute if error Error_Number had occurred}
Catch Is <RelationalOperator> Error_Number {statements to execute if the condition is true}
Catch Error_Number1 To Error_Number2 {statements to execute if error number is between values}
Catch Else {statements to execute if all other errors had occurred}
where:
The number of Catch statements is not explicitly limited.
Error_Numbers can only be long-type numeric values.
In Catch…To…, if Error_Number1 > Error_Number2, the catch statement is never true and no error is flagged.
Catch statements are used within three types of error trapping blocks.
The Try block is designed to trap synchronous errors within task context (For more details, see the Error Handling section). There is no explicit limitation on the number of Try blocks instances in a program. The syntax for a Try block is:
Try
{code being examined for synchronous errors}
{Catch Error_Number {statements to be executed}}
{Catch Is <RelationalOperator> Error_Number {statements to be executed}}
{Catch Error_Number1 To Error_Number2 {statements to be executed}}
{Catch Else {statements to be executed}}
{Finally {statements to be executed if an error was trapped}}
End Try
An example of a Try block, designed to catch errors in the loading process of Task1.Prg:
Try Load Task1.Prg Catch 4033 ‘ File does not exist Print “Task not found” Catch 6007 ‘ Task must be killed first KillTask Task1.Prg Unload Task1.Prg Load Task1.Prg Catch Else Print “Error while loading Task1.Prg” Finally Print “Caught error: “ Task1.prg.Error End Try
The OnError block is designed to trap and process both synchronous and asynchronous errors in a task. OnError traps errors not trapped by the Try/Finally mechanism within the task. (For more details, see “Error Handling” section). Only one instance of OnError may exist in a program. The syntax for OnError block is:
OnError
{Catch Error_Number {statements to be executed}}
{Catch Is <RelationalOperator> Error_Number {statements to be executed}}
{Catch Error_Number1 To Error_Number2 {statements to be executed}}
{Catch Else {statements to be executed}}
End OnError
An example of an OnError block, designed to stop motion in case of a motion error:
OnError
Catch 3001 To 3999 ‘ Motion errors
System.Motion = 0
A1.Enable = 0
? VESExecute("System.Motion = 1")
A1. Enable = 1
Print "Caught a Motion error: " ThisTask.Prg.Error
Catch Else
Print "Caught a non-Motion error: " ThisTask.Prg.Error
End Onerror
The OnSystemError block is designed to trap and process both synchronous and asynchronous errors in all tasks, as well as errors that occur within the context of the system (For more details, see the Error Handling section). Only one instance of OnSystemError may exist in the system. The syntax for OnSystemError block is:
OnSystemError
{Catch Error_Number {statements to be executed}}
{Catch Is <RelationalOperator> Error_Number {statements to be executed}}
{Catch Error_Number1 To Error_Number2 {statements to be executed}}
{Catch Else {statements to be executed}}
End OnSystemError
An example of an OnSystemError block, designed to monitor errors in task Errors.Prg:
OnSystemError Catch Is < 12000 Print “Caught a MC error: ” System.Error ‘ MC errors KillTask Errors.Prg Catch Is > 20000 Print “Caught a user error: ” System.Error ‘ User defined errors KillTask Errors.Prg End OnSystemError
Nesting
Program control commands can be nested. Nesting is when one program control command (or block of commands) is within another. There is no specified limit on the number of levels of nesting.
For example, the following program nests a WHILE…END WHILE sequence within a FOR…NEXT sequence:
For I = 1 to 10 N=5 While N>0 N=N-1 'This command will be executed 50 times End While Next I
There is no specified limit on the number of levels of nesting. The Sample Nesting Program in Appendix A shows numerous combinations of nesting.
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