Manual

Detailed Descriptions of ACL Commands 3-55
PD [<delay>, <new> [, <which>]] Pre-Move Digital Outputs Changes
The PD command establishes Digital Outputs changes and delays which are to occur before
each subsequent AA, AR, MA, MR, MT, or Continuous Path move until another PD
command is executed. This is the equivalent of executing a CD command and a WA
command before each move. However, with PD the delay between the Outputs change and
the beginning of motion is precisely controllable and cannot be interrupted, for example, by
pressing the PAUSE button at the wrong moment.
Each Digital Output can only have one value at a time, either True or False (one or zero).
The CD and TD commands change the outputs immediately; the PD command causes the
outputs to change later, when X/Y motion is performed. Once an output has been changed
either by a CD or TD or by a move after a PD, MD, or MM, the old value of that output is
forgotten.
PD can be used with the MD or MM commands to establish up to 33 Digital Outputs
changes to be performed before and during each move.
After power up and IN, and if a PD with no parameters is executed, pre-move Digital
Outputs changes are disabled. They can also be temporarily disabled via the VM command.
<delay> is optional; it is the number of seconds to wait after changing the Outputs, before
beginning the motion. It can be in the range 0 through 6.5535, with a resolution of 0.0001
second. If <delay> is zero then the PD command is equivalent to an MD or MM command
with a <count1> of zero. In other words, the Outputs change just before the first step is
taken. If both a PD 0,... and an MD 0,... or MM 0,... are active then the PD's value is
output approximately 40 microseconds before the MD's or MM's first value.
If <delay> is specified then <new> must also be specified.
<new> and <which> determine the new values to be written to the Digital Outputs. For
information about the range and meaning of these parameters please see the <new> and
<which> parameters of the CD command.
If <which> is omitted it defaults to 255 (i.e. binary 11111111), meaning that all 8 Digital
Outputs are affected by the value of <new>. <which> cannot be specified unless <delay>
and <new> are also specified.
A zero-length move (for example, due to MR 0, 0; two MA's to the same point, or an arc
with zero radius or sweep angle) produces the specified Outputs change and delay, but no
motion.
Only one PD command at a time can be active; a PD cancels the parameters of any
preceding PD.
If the machine is in the Emergency Stopped state when an AA, AR, MA, or MR occurs the
motion command is ignored. Therefore no PD-induced change occurs at the Digital
Outputs. If an Emergency Stop occurs during a move the Digital Outputs all go immediately
to the False state.
The effects of the PD command can be suspended for a single move or group of moves
through use of the VM command.