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152 • Chapter 7 Application Programming DMC-1700/1800
Example - Command Error
#BEGIN Begin main program
IN “ENTER SPEED”, SPEED Prompt for speed
JG SPEED;BGX; Begin motion
JP #BEGIN Repeat
EN End main program
#CMDERR Command error utility
JP#DONE,_ED<>2 Check if error on line 2
JP#DONE,_TC<>6 Check if out of range
MG “SPEED TOO HIGH” Send message
MG “TRY AGAIN” Send message
ZS1 Adjust stack
JP #BEGIN Return to main program
#DONE End program if other error
ZS0 Zero stack
EN End program
The above program prompts the operator to enter a jog speed. If the operator enters a number out of range (greater
than 8 million), the #CMDERR routine will be executed prompting the operator to enter a new number.
In multitasking applications, there is an alternate method for handling command errors from different threads.
Using the XQ command along with the special operands described below allows the controller to either skip or retry
invalid commands.
OPERAND FUNCTION
_ED1 Returns the number of the thread that generated an error
_ED2 Retry failed command (operand contains the location of the failed command)
_ED3 Skip failed command (operand contains the location of the command after the
failed command)
The operands are used with the XQ command in the following format:
XQ _ED2 (or _ED3),_ED1,1
Where the “,1” at the end of the command line indicates a restart; therefore, the existing program stack will not be
removed when the above format executes.
The following example shows an error correction routine which uses the operands
.
Example - Command Error w/Multitasking
#A Begin thread 0 (continuous loop)
JP#A
EN End of thread 0
#B Begin thread 1
N=-1 Create new variable
KP N Set KP to value of N, an invalid value
TY Issue invalid command
EN End of thread 1