Reference Manual

Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 88
value for its starting position, and a potentially dangerous jump will occur.
(PMATCH is automatically executed on an R (run) or S (step) command.)
Ixx07 Motor xx Master (Handwheel) Scale Factor
Range: -8,388,608 - 8,388,607
Units: none
Default: 96
Ixx07 controls with what scaling the master (handwheel) register gets multiplied when extended into the
full-length register. In combination with Ixx08, it controls the following ratio of Motor xx for position
following (electronic gearing) according to the equation:
tionMasterPosi
08Ixx
07Ixx
ionMotorPosit  
For this position-following function, Ixx07 and Ixx08 can be thought of as the number of teeth on
meshing gears in a mechanical coupling.
Ixx07 may be changed on the fly to permit real-time changing of the following ratio, but Ixx08 may not.
Ixx08 should therefore be set to a large enough value to get the required fineness of ratio changes.
Ixx08 Motor xx Position Scale Factor
Range: 0 - 8,388,607
Units: none
Default: 96
Ixx08 specifies the multiplication scale factor for the internal position registers for Motor xx. Source
position registers are multiplied by Ixx08 as the get extended into the full-length motor position registers.
For most purposes, this is transparent to the user and Ixx08 does not need to be changed from the default.
There are two reasons that the user might want to change this from the default value. First, because it is
involved in the gear ratio of the position following function -- the ratio is Ixx07/Ixx08 – the value of
Ixx08 might be changed (usually raised) to get a more precise ratio.
The second reason to change this parameter (usually lowering it) is to prevent internal saturation at very
high gains or count rates (velocity). PMAC's filter will saturate when the velocity in counts/sec
multiplied by Ixx08 exceeds 768M (805,306,368), or 256M (268,435,456) in PVT mode. This only
happens in very rare applications -- the count rate must exceed 8.3 million counts per second (2.8 million
in PVT mode) before the default value of Ixx08 gives a problem.
Note:
When changing this parameter, make sure the motor is killed (disabled).
Otherwise, a sudden jump will occur, because the internal position registers will
have changed. This means that this parameter should not be changed in the middle
of an application. If a real-time change in the position-following gear ratio is
desired, Ixx07 should be changed.
In most practical cases, Ixx08 should not be set above 1000 because higher values can make the servo
filter saturate too easily. If Ixx08 is changed, Ixx30 should be changed inversely to keep the same servo
performance (e.g. if Ixx08 is doubled, Ixx30 should be halved).
Ixx09 Motor xx Velocity-Loop Scale Factor
Range: 0 - 8,388,607
Units: none
Default: 96