Reference Manual

PMAC 2 Software Reference
PMAC I-Variable Specification 143
I9n3 Capture n Flag Select Control {PMAC2 only}
Range
0 .. 3
Units
none
Default
0
Remarks
This parameter determines which of the “Flag” inputs will be used for position capture (if
one is used – see I902 etc.):
..........................0: HMFLn (Home Flag n)
..........................1: PLIMn (Positive End Limit Flag n)
..........................2: MLIMn (Negative End Limit Flag n)
..........................3: USERn (User Flag n)
Typically, this parameter is set to zero, because in actual use the LIMn flags create other
effects that usually interfere with what is trying to be accomplished by the position
capture. If you wish to capture on the PLIMn or MLIMn flags, you probably will want to
disable their normal functions with Ix25, or use a channel n where none of the flags is used
for the normal axis functions.
I9n4 Encoder n Gated Index Select {PMAC2 only}
Range
0 .. 1
Units
none
Default
0
Remarks
I9n4 controls whether the “raw” encoder index signal is used for the position capture of the
channels’ encoder counter, or whether the quadrature signals of the encoder are first used
to create a pulse that is a single quadrature state wide. When I9n4 is set to 0, the encoder
index channel input (CHCn) is passed directly into the position capture circuitry.
When I9n4 is set to 1, the encoder index channel input (CHCn) is logically combined with
(“gated by”) the quadrature signals of Encoder n before going to the position capture
circuitry. The intent is to get a “gated index” signal exactly one quadrature state wide.
This provides a more accurate and repeatable capture, and makes the use of the capture
function to confirm the proper number of counts per revolution very straightforward.
In order for the gated index capture to work reliably, the index pulse must reliably span
one, but only one, “high-high” or “low-low” AB quadrature state of the encoder. I9n5
allows you to select which of these two possibilities is used.
Note:
If I9n4 is set to 1, but I9n2 bit 0 is set to 0, so the index is not used
in the position capture, then the encoder position is captured on the
first edge of any of the U, V, or W flag inputs for the channel. In
this case, bits 0, 1, and 2 of the channel status word tell what hall-
state edge caused the capture.