Application Notes

Intro to MCode : Program and Language Structure

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Description

This Application Note covers the basic structure and programming conventions of the MCode language, The differences between Liberty* MCode and MDrive MCode is primarily found in the syntax of the I/O instructions.

 

Applicable

  • Liberty* MDrive
  • MDrive Linear Actuator
  • MDrive Plus
  • MForce

Requirements

  1. PC with the Motion Control Programmer installed
  2. A Liberty* MDrive Motion Control connected to power and communications.

*Previously Lexium

Details

Basic structure of the MCode language

Liberty* MCode consists of 1 and 2 character mnemonics which access all the features and functions of the Motion Control product family. These mnemonics are clearly identified as to their function. i.e. VI (Initial Velocity), A (Acceleration), MS (MicroStep resolution) and etc. HINT: :Liberty* MCode commands ARE NOT Case sensitive. They may be upper or lower case. There are five basic components of the Liberty* MCode programming language, they are:

  1. Instructions
  2. Variables
  3. Flags
  4. Keywords
  5. Math functions
Instructions

Instructions

An instruction results in an action. There are four types of instructions:

  1. Motion
  2. I/O
  3. Program
  4. System

The examples below will not show every instruction example, just the most commonly used.

Motion instructions

Motion instructions are those that result in the movement of a motor. The syntax for these commands is as follows: type the command followed by a space, and then the velocity or position data. Example motion instructions

MnemonicFunctionUsage exampleDescription
MAMove to an absolute positionMA 51200Move abs position 51200
MRMove to a relative positionMR 51200Move relative 51200 steps
SLSlew axis at constant velocitySL 20000Slew at 20000 steps/sec
HMHoming mode set upHM 1Set homing mode to mode 1

I/O instructions

Lexium Motion Products MDrive Motion Products

Liberty* MDrive I/O Instructions

An I/O instruction results in the change of parameters or the state of an input or output. The syntax for these commands are as follows: type the command then an equal sign, then the data. Example: O2=0 will set output 2 to 0. Example I/O instructions

MnemonicFunctionUsage exampleDescriptionIsSet an input point type and active stateIs=1,0,0Set input 1 to be general purpose active LOWOsSet an output point type and active stateOs=1,16,0Set output 1 to be general purpose active LOWI<input>Read an individual input state as 1 or 0PR I4Read the state of input 4CL k3, I4=1Call subroutine k3 when I/O 4 is HIGH (1)O<output>Set the logic state of an individual outputO3=1Set output 3 HIGH (1)

MDrive Motion Products

An I/O instruction results in the change of parameters or the state of an input or output. The syntax for these commands are as follows: type the command then an equal sign, then the data. Example: O2=0 will set output 2 to 0.

Example I/O instructions

MnemnonicFunctionUsage exampleDescription
S<io point>Set I/O point type, active state and to sink or sourceS1=2,1,0Set I/O 1 to be a Limit+ input, active when high, sinking.
I<io point>Read an individual input state as 1 or 0PR I4Read the state of input 4
CL k3,I 4=1Call subroutine k3 when I/O 4 is HIGH (1)
O<io point>Set the logic state of an individual outputO3=1Set output 3 HIGH (1)

Program instructions

A program instruction allows program manipulation. The syntax of these vary due to the nature of the command. Some command examples would be: PG 100, which toggles the system into program mode starting at address 100; BR LP, I1=1, which will branch to a program labeled LP if input 1 is true. Example program instructions

MnemonicFunctionUsage exampleDescription
PGEnter/exit program modePG 100Begin program at address 200
LBLabel program, subroutine or branch processLB k1Label subroutine k1
LB SULabel program to run at startup (SU is a keyword for this action)
BRUsed to branch conditionally or unconditionally) to a routine or processBR k1Unconditional branch to process k1
BR k1, I1=1Conditional branch to process k1 if I/O 1 = 1
CLCall subroutine conditionally or unconditionallyCL Q2Unconditionally call subroutine Q2
CL Q2, R1>1Conditionally call subroutine Q2 if register 1 is greater than 1
HHold program executionHHold program execution until motion completes
h 1000Hold program execution for 1 second
EDesignates the end of a programEEnd program

System instructions

A system instruction is an instruction that can only be used in immediate mode to perform a system operation such as program execution (EX) or listing the contents of program memory (L). For example: EX 100 will execute a program located at address 100 of program memory space, or EX K1 will execute a program labeled K1. Example program instructions

MnemonicFunctionUsage exampleDescription
CPClear program memory spaceCP 100Clear program memory starting at address 100
EXExecute programEX G1Execute program labeled G1
SSaveSSave all parameters and programs
FDRestore factory default settingsFDRestore factory defaults
Variables

Variables

A Variable is identified by a mnemonic and allows the user to define or manipulate data. These can also be used with the math functions to manipulate data. There are two classes of variables: factory-defined and user-defined. There are 192 user program labels and variables available. The syntax for each variable may differ.

Factory defined variables

These variables are predefined at the factory. They cannot be deleted. When an FD (Factory Default) instruction is given, these variables will be reset to their factory default values. There are two types of factory defined variables:

  • Read/write – variables that may have their value altered by the user to effect events in a program.
    • P (position counter) can be set i.e. P=0 or read, i.e PR P.
    • A (acceleration) can be changes as part of a move profile i.e. A=200000 steps/sec^2.
  • Read only – Variables whose value cannot be modified by the user, but may be read or used to effect program events.
    • V (velocity register the current velocity of the axis in steps/second.

User defined variables

The VA instruction allows the user to create a 2 character name to a user defined variable (32 bit value). When and FD (Factory Default) is given, user defined variables are deleted. The restrictions for this command are:

  1. A user variable must have a unique name, it cannot be named after an MCode command,
  2. The first character must be alpha, the second may be alpha-numeric, i.e. K1, Ga, Z3 etc.
    HINT: The following Alpha characters are not used by any MCode command: G, K, X, Y or Z. A best practice is to name all user variables and program/subroutine labels with one of these alpha characters followed by a number.
  1. Two character limit.

There are two types of user defined variables:

  1. Global variables – global variables are variables that are defined outside of a program. The benefit t to using a global variable is that no user program memory is required.
  2. Local variables – this type of user defined variable is defined within a program and can only affect events within that program. It is stored in RAM. Note a local variable is not static, but is erased and declared again each time a program is executed.

Commonly used variables

MnemonicFunctionUsage exampleDescription
AAccelerationA=200000Set Acceleration to 200000 steps/sec^2
DDecelerationD=ASet deceleration equal to acceleration
MSMicrostep resolutionMS=2Set microstep resolution to 400 steps/rev (half-step)
PPositionP=0Set position counter to 0
VIInitial velocityVI=1000Set initial velocity to 1000 steps/sec
VMMaximum velocityVM=10000000Set max velocity to 10000000 steps/sec
Keywords

Keywords

Keywords are used in conjunction with the PR and IP instructions to indicate or control variables and flags. For instance, PR UV would print the state of all the user-defined variables to the screen. IP would restore all the factory variables from the NVM.

Math Functions

Math functions

Math functions are used to perform various arithmetic functions on numeric data stored in registers or variables. Supported functions are +, -, x, ÷, >, <, =, ≤, ≥, AND, OR, XOR, NOT. For purposes of the following examples we will use registers R1-R4) and user variables labeled k1….kn for illustrating the use of math functions, though any variable may be used.

SymbolFunctionDescriptionUsage example
+AdditionAdd variablesR1=k1+k2
–SubtractionSubtract variablesR1=k1-k2
*MultiplyMultiply to variablesR1=k1*k2
/DivisionDivide two variablesR1=k1/k2
<>Not equalPerform action if variable is not equal to variable or integerBR G1, k1<>1 CL Z2, k1<>1
=Equal toPerform action if variable is equal to variable or integerBR G1, k1=1 CL Z2, k1=0
<Less thanPerform action if variable is less than a variable or integerBR G1, k1<k2 CL Z2, k1<50
<=Less than or equal toPerform action if variable is less than or equal to a variable or integerBR G1, k1<=k2 CL Z2, k1<=50
>Greater thanPerform action if variable is greater than a variable or integerBR G1, k1>k2 CL Z2, k1>50
>=Greater than or equal toPerform action if variable is greater than or equal to a variable or integerBR G1, k1>=k2 CL Z2, k1>=50
&AND (bitwise)Perform a bitwise AND operationR1=k1&k2
|OR (bitwise)Perform a bitwise OR operationR1=k1|k2
^XOR (bitwise)Perform a bitwise XOR operationR1=k1^k2
!NOT (bitwise)Perform a bitwise NOT operationR1=k1!k2
Program Structure

Programming Aids

FunctionDescriptionUsage example
User labelsThe MCode programming language allows for 192 user labels for your programs, subroutines, and user variables and flags. A label consists of 2 characters, the first of which must be a letter, the second may be alphanumeric. A label cannot use the same character combination as any of the mnemonics used in the MCode programming languagePG LB G1 – label program as G1VA K3 – label user variable K2LB Qa – label subroutine as Qa
Comment character (‘)MCode allows for comments to be inserted in your program code. The comment character for the MCode language is the Apostrophe (‘). The device will ignore the text string following the apostrophe. Please note that the maximum length of a single line of program code is 64 characters, this includes program text, spaces and comments.‘ this is a comment PG 100 ‘ enter program mode at address 100 LB G1 ‘label program G1

Program Structure

Proper structuring of your MCode program will ensure your ability to work efficiently and will aid in trouble shooting your program. The figure below illustrates how your program can be blocked out to group the global system declarations, the main program body and the subroutines.

Bring it all together

Here is a simple program that, when executed, perform a move and print the position. Once entered, from immediate mode enter “EX G1” to run the program.

 

*Previously Lexium

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