Omron GRT1-ML2 Hardware Reference Manual page 23

System philosophy
2.2.4 Other operations
Cancelling moves
In normal operation or in case of emergency it can be necessary to cancel
the current movement from the buffers. When the CANCEL or RAPIDSTOP
commands are given, the selected axis respectively all axes will cancel their
current move.
Origin search
The encoder feedback for controlling the position of the motor is
incremental. This means that all movement must be defined with respect to
an origin point. The DATUM command is used to set up a procedure
whereby the TJ1-MC__ goes through a sequence and searches for the
origin based on digital inputs and/or Z-marker from the encoder signal.
Print registration
The TJ1-MC__ can capture the position of an axis in a register when an
event occurs. The event is referred to as the print registration input. On the
rising or falling edge of an input signal, which is either the Z-marker or an
input, the TJ1-MC__ captures the position of an axis in hardware. This
position can then be used to correct possible error between the actual
position and the desired position. The print registration is set up by using the
REGIST command.
The position is captured in hardware, and therefore there is no software
overhead and no interrupt service routines, eliminating the need to deal with
the associated timing issues.
HARDWARE REFERENCE MANUAL 18