Reference Manual

PMAC 2 Software Reference
140 PMAC I-Variable Specifiation
Channel-Specific Gate Array I-Variables
(For Channel n, where n = 1 to 8)
I-Variables in the I910s through I980s control the hardware aspects of the “DSPGATE1” ASICs that
provide the machine interface for channels 1 through 8. Each DSPGATE1 ASIC controls four channels.
On an 8-channel PMAC2 (one that includes Option 1), I-variables for all 8 channels can be used. On a 4-
channel PMAC2 (PMAC2-Lite or other PMAC2 without Option 1), only the I-variables for the first 4
channels can be used. On a PMAC2 Ultralite, there are no local machine interface channels, so none of
the I-variables in this range may be used.
Note:
In almost all cases, the machine interface channel n used for Motor x will be of the
same number as the motor number (that is, n = x). However, this does not
necessarily have to be the case, so it is a good idea to keep a clear distinction
between the software motor functions and the hardware channel functions.
There are no I-variables for the Channels 9 – 16 that come on an ACC-24P/V2 board. Setup of these
channels must be done with M-variables assigned to the appropriate control registers of these channels,
and values assigned to these M-variables after every board power-up.
I9n0 Encoder/Timer n Decode Control {PMAC2 only}
Range
0 .. 15
Units
None
Default
7
Remarks
I9n0 controls how the input signal for Encoder n is decoded into counts. As such, this
defines the sign and magnitude of a “count”. The following settings may be used to
decode an input signal.
Setting Meaning
0 Pulse and direction CW
1 x1 quadrature decode CW
2 x2 quadrature decode CW
3 x4 quadrature decode CW
4 Pulse and direction CCW
5 x1 quadrature decode CCW
6 x2 quadrature decode CCW
7 x4 quadrature decode CCW
8 Internal pulse and direction
9 (reserved for future use)
10 (reserved for future use)
11 x6 hall decode CW
12 MLDT pulse timer control
13 (reserved for future use)
14 (reserved for future use)
15 x6 hall decode CCW
In any of the quadrature decode modes, PMAC2 is expecting two input waveforms on
CHAn and CHBn, each with approximately 50% duty cycle, and approximately one-
quarter of a cycle out of phase with each other. Times-one (x1) decode provides one count
per cycle; x2 provides two counts per cycle; and x4 provides four counts per cycle. The
vast majority of users select x4 decode to get maximum resolution.