ElmoMC SimplIQ Digital Servo Drives-Bell Command Reference - Manual (Page 253)

An unused part of the PVT table may be programmed for the next motion while the
present motion is executing. An attempt to modify the data of an executing motion
segment generates an error.
6.1.6.3 Mode Termination
PVT motion terminates upon one of the following events:
The motor is shut down, either by programming MO=0 or by an exception.
Another mode of motion is set active; by programming PA=xxx; BG, for example.
In this case, the new motion command executes immediately, without having to
explicitly terminate the PVT mode.
The PVT motion manager runs out of data. This occurs when the read pointer
reaches MP[2] and MP[3] is zero. This may also occur in auto-increment mode
(CAN communications only) if the read pointer reaches the write pointer. In that
case, the PVT motion is stopped immediately, using the SD deceleration. Note
that if the last programmed PVT speed is zero, the PVT motion terminates neatly
and the stop at the end of the motion does nothing.
6.1.6.4 PVT Motion Using CAN
The PVT table allows for the performance of both pre-designed and online motion plans.
For online motion design, new entries can be written to the PVT table while the PVT
motion is executing. The online motion design ability is limited by the speed of the
communication interface.
With an RS-232 ASCII communication interface, a single PVT table row is programmed
with the following format:
QP[xx] = xxx,xxx,xxx; QV[xx] = x,xxx,xxx; QT[xx] = xxx;
Up to 40 characters may be required to program a single PVT table row. At a
communication rate of 19,200 baud, this may take 20 milliseconds. At a communication
rate of 115,200 baud, this may take 4 milliseconds.
The CAN communication option allows much faster PVT table programming, by packing
an entire PVT table row into one PDO communication packet. For easy synchronization
with the host, the drive may be programmed to send the PVT read and write pointers
continuously to the host as a synchronous PDO, or to send an emergency object
whenever the number of as yet unexecuted motion segments falls below a given
threshold.
SimplIQ for Steppers Application Note The Position Reference Generator
MAN-STECR (Ver. 1.1)
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