High Speed Position Capture (The Latch Function); Fast Update Rate Mode - Galil Motion Control DMC-18 2 Series User Manual

High Speed Position Capture (The Latch Function)

Often it is desirable to capture the position precisely for registration applications. The DMC-18x2
provides a position latch feature. This feature allows the position of the encoder of X,Y,Z, or W to be
captured upon the state change of an external input signal. The general inputs 1 through 4 correspond
to each axis.
IN1 X-axis latch
IN2 Y-axis latch
IN3 Z-axis latch
IN4 W-axis latch
Note: The inputs are TTL. Latch time is less than 1 µsec. (high or low going)
The DMC-18x2 software commands AL and RL are used to arm the latch and report the latched
position. The steps to use the latch are as follows:
1. Give the AL XYZW command to arm the latch for the encoder.
2. Test to see if the latch has occurred (Input goes low) by using the _AL X or Y or Z or W
3. After the latch has occurred, read the captured position with the RL XYZW command or
Note: The latch must be re-armed after each latching event.
Example:
#Latch
JG,5000
BG Y
AL Y
#Wait
JP #Wait,_ALY=1
Result=_RLY
Result=
EN

Fast Update Rate Mode

The DMC-18x2 can operate with much faster servo update rates than default operation or standard
operation. This mode is known as 'fast mode' and allows the controller to operate with the following
update rates:
DMC-1812
DMC-1822
DMC-1832
DMC-1842
106 ● Chapter 6 Programming Motion
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1 through 4:
command. Example, V1=_ALX returns the state of the X latch to the variable V1. V1 is
1 if the latch has not occurred.
_RLXYZW.
Latch program
Jog Y
Begin motion on Y axis
Arm Latch for Y axis
#Wait label for loop
Jump to #Wait label if latch has not occurred
Set value of variable 'Result' equal to the report position of y axis
Print result
End
125 usec
125 usec
250 usec
250 usec
DMC-18x2