ElmoMC SimplIQ Software Manual - Manual (Page 160)

SimplIQ Software Manual The Position Reference Generator
MAN-SIMSW (Ver. 1.4)
11-19
This flow differs from the basic mode because:
ƒ
The motion queue underflow is diagnosed by the read pointer reaching the write
pointer.
ƒ Emergency objects are issued for the queue low and queue underflow events.
Programming Sequence for Auto-increment PVT Mode
PVT motion must begin with the initial programming of the PVT arrays. To do so, set:
MP[1] = First valid line in PVT table
MP[2] = Last valid array in PVT table
MP[3] = 1 for cyclical mode
MP[4] = Not relevant for PVT (PT only)
MP[5] = Number of remaining programmed motion rows for issuing a “PVT queue low”
emergency object. Set to zero if no “PVT queue low” warning is desired.
MP[6] = Write pointer. This is the next position in the PVT table to be written by the
CANopen object 0x2001.
Set the QP[N], QV[N] and QT[N] array elements for at least the first two rows of the PVT
table. This is needed because PVT requires at least two time points for interpolating the
motion trajectory.
If not already set, set UM=4 or UM=5, and MO=1.
Set PV=N, assuming QP[N], QV[N], QT[N] and QP[N+1], QV[N+1], QT[N+1] are all
programmed to valid values.
Start the motion with a BG.
Use the CAN PVT auto-increment command for the rest of the PVT motion.
When object 0x2001 is used to feed PVT reference points to the drive while a PVT motion
is executing, the drive automatically enters Online Feed mode, in which the drive is
aware of the position written and takes the following precautions:
ƒ
If the feed is too slow, so that the drive must fetch unprogrammed points, the motion
will abort with a “Queue underflow” emergency.
ƒ If the feed is too fast, so that points not yet used by the drive are overstruck, the drive
will reject the feed attempt with a “Queue overflow” emergency.
The Online Feed mode will continue until the end of the current PVT motion and will not
be applied to the next motion.
To stay informed about how the PVT motion is advancing, the read and write PVT table
pointers can be received continuously, mapped to a synchronous PDO, or the “Queue
low” emergency signal can be used to indicate the need for more data. The “Queue low”
emergency message includes the present location of the read pointer and the write
pointer. It is safe to send more PVT data PDOs until the write pointer is one location
before the read pointer specified by the “Queue low” emergency message.
The host is well aware of the location of the write pointer, because it can count its own
messages. However, a data message may be rejected because the queue is full, or because
a message has been lost. In such a case, the drive issues an emergency object to the host.
After receiving the object, the true location of the write pointer may be unclear. The host
may then set MP[6] to the possibly-rejected table row and continue writing from there.