? Read controller motion status

Command	Command description	Controller response	Default mode (N/A - not available)	Service Mode (N/A - not available)
x?	Is the controller ready to accept next motion command?	1 = ready. 0 = still busy, -1 = error detected, use ER command to get error explanation	Yes	Yes

SYNTAX    x?, where x - controller number.
PARAMETER none.
DESCRIPTION This command is used to test the controller current motion status.
Note: Use the command to know when the motion is finished. Send to controller next motion command if the stepper motor is idle. Motion commands are: MV, SH, ST, OR.
RETURNS 0 || 1 || -1
0  Wait. Controller is busy.
1  Ready. Controller is idle. Stepper motor is not moving. Controller is waiting for next motion command.
-1 Motion error detected. No more motion is enabled until user reads error code by ER command.
REL. COMMANDS none.
EXAMPLES: 5?   ||  3 ? ||   1000?