Galil DMC-1800, DMC-1700 user manual Example - Command Error w/Multitasking

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

152 • Chapter 7 Application Programming DMC-1700/1800