Reference Manual

PMAC 2 Software Reference
146 PMAC I-Variable Specifiation
1 = Invert direction signal (- = low; + = high)
I9n8 controls the polarity of the direction output signal in the pulse-and-direction format
for Channel n. It is active only if I9n6 has been set to 2 or 3 to use Output C as a pulse-
frequency-modulated (PFM) output.
If I9n8 is set to the default value of 0, a positive direction command provides a low output;
if I9n8 is set to 1, a positive direction command provides a high output.
I9n9 Channel n Hardware-1/T Control {PMAC2 only}
Range
0 – 1
Units
none
Default
0
Remarks
I9n9 controls whether the “hardware-1/T” functionality is enabled for a PMAC2 Servo IC
on Channel n. If I9n9 is set to the default value of 0, the hardware-1/T functionality is
disabled, permitting the use of the “software-1/T” position extension that is calculated by
default with encoder conversion method $0. If I9n9 is set to 1, the hardware-1/T
functionality is enabled (if present on the IC), and the software-1/T cannot be used.
The hardware-1/T functionality is present only on Revision D and newer of the PMAC2-
style DSPGATE1 IC, released at the beginning of the year 2002. Setting I9n9 to 1 on an
older revision IC does nothing – software-1/T functions can still be used.
When the hardware-1/T functionality is enabled, the IC computes a new fractional-count
position estimate based on timers every SCLK (encoder sample clock) cycle. This permits
the fractional count data to be used for hardware capture and compare functions, enhancing
their resolution. This is particularly useful when the IC is used on an ACC-51 high-
resolution analog-encoder interpolator board. However, it replaces the timer registers at
the first two “Y” addresses for the channel with fractional count position data, so the
traditional software-1/T method of the conversion table cannot work if this is enabled.
If you enable the hardware-1/T functionality, and want to be able to use 1/T interpolation
in your servo loop, you must use the hardware-1/T extension method ($C method digit
with the mode switch bit set to 1) in the encoder conversion table.
PMAC2 DSPGATE2 I-Variables
I-Variables numbered in the I990s control hardware aspects of the “DSPGATE2” ASIC. This IC controls
operation of the MACRO ring on all PMAC2 boards. On the Ultralite versions of the PMAC2, this IC
also controls the frequency of the clock signals on the board, because the “DSPGATE1” ICs are not
present. On all of these boards, I990 and I991 control the decode of the handwheel encoder inputs on the
JHW port.
I990 Handwheel 1 Decode Control {PMAC2 only}
Range
0 .. 15
Units
none
Default
7
Remarks
I990 controls how the input signal for Handwheel 1 on the JHW port 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.
0: ......................Pulse and direction CW
1: ......................x1 quadrature decode CW
2: ......................x2 quadrature decode CW