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BG starts the motion.
The QP vector may be written on-line while a PT motion is on, as long as you don't program presently
executing PT elements.
12.1.7.5 Mode Termination
The PT motion terminates upon one of the following cases:
The motor is shut down, either by programming MO=0 or by an exception.
Another mode of motion is set active, e.g. by programming PA=xxx;BG. In this case the new motion
command executes immediately, without having to explicitly terminate the PT mode.
The PT motion manager runs out of data. This happens when the read pointer reaches MP[2] and
MP[3] is zero. This may also happen in the auto increment mode (CAN communications only, see
below) if the read pointer reaches the write pointer. Then the PT motion is stopped immediately,
using the SD deceleration. Note that if the last programmed PT speed is zero, then the PT motion
terminates neatly.
12.1.7.6 PT Motion Using CAN
The PT table allows the performance of pre-designed motion plans, as well as the on-line design of motion
plans by writing the QP vector while PT motion is executing.
The on-line motion design ability is limited by the speed of communication interface.
Consider an RS-232 ASCII communication interface.
Programming of a single QP vector element has the format
QP[xx]=xxxxxxxxx;
Up to 18 characters may be required to program a single position point.
At the communication rate of 19200 baud, this may take 9msec, and 1.8msec at the baud rate of 115200.
The CAN communication option allows much faster PT programming, by packing two position points into
one PDO communication packet. For easy synchronization with the host, the Amplifier may be programmed
to send the PT read and write pointers continuously to the host as a synchronous PDO, or to send an
emergency object whenever the number of yet unexecuted motion segments falls below a given threshold.
12.1.7.7 The PT Motion Programming Message
Two positions for the QP vector can be programmed in the eight bytes of a single PDO.
The PDO used is 0x300+ID where ID is the node ID of the Amplifier. Note that before using PDO
0x300+ID for PT, its PDO mapping must be first set correctly.
The mapping of this PDO for the PT mode is listed in the table below.
Object Dictionary Index 0x2002
Type RECORD, 2 elements
Access Write only
Structure: Signed32 Position1
Signed32 Position2
PDO mapping Yes
Value limits No
Default value Not Applicable
Note that the PDO does not specify the QP vector elements to be programmed.
The elements to be programmed are specified by a “write pointer”.
The value of the write pointer may be set by the parameter MP[6].
The value of the write pointer may be set once for the entire motion. The write pointer is incremented
automatically by two each time the amplifier receives a new PT motion-programming message.
The CAN auto increment mode has the following flow diagram: