Reference Manual

Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 221
In other Turbo PMAC2 systems, to change which IC is the source of the system clocks, it is best to
change both clock-direction I-variables on a single command line (e.g. I6807=1 I7007=0), then
SAVE these new settings.
If all of the Servo and MACRO ICs in a Turbo PMAC2 system have been set up for external Phase and
Servo clocks, but these clock signals are not provided, the Turbo PMAC2 will immediately trip its
watchdog timer.
For accessory boards in which alternate addressing of the Servo IC is used (labeled Servo IC m*), this
function is controlled by I7m57, not I7m07.
PMAC2-Style Channel-Specific Servo IC I-Variables
(For Servo IC m Channel n, where m = 0 to 9, and n = 1 to 4)
I7mn0 Servo IC m Channel n Encoder/Timer Decode Control
Range: 0 - 15
Units: None
Default: 7
I7mn0 controls how the input signal for Encoder n on a PMAC2-style Servo IC m 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.
 I7mn0 = 0: Pulse and direction CW
 I7mn0 = 1: x1 quadrature decode CW
 I7mn0 = 2: x2 quadrature decode CW
 I7mn0 = 3: x4 quadrature decode CW
 I7mn0 = 4: Pulse and direction CCW
 I7mn0 = 5: x1 quadrature decode CCW
 I7mn0 = 6: x2 quadrature decode CCW
 I7mn0 = 7: x4 quadrature decode CCW
 I7mn0 = 8: Internal pulse and direction
 I7mn0 = 9: Not used
 I7mn0 = 10: Not used
 I7mn0 = 11: x6 hall-format decode CW*
 I7mn0 = 12: MLDT pulse timer control
(internal pulse resets timer; external pulse latches timer)
 I7mn0 = 13: Not used
 I7mn0 = 14: Not used
 I7mn0 = 15: x6 hall-format decode CCW*
*requires version B or newer of the DSPGATE1 Servo IC.
In any of the quadrature decode modes, the Servo IC 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.
The clockwise (CW) and counterclockwise (CCW) options simply control which direction counts up. If
the wrong direction sense is received, simply change to the other option (e.g. from 7 to 3 or vice versa).
WARNING:
Changing the direction sense of the decode for the feedback encoder of a motor
that is operating properly will result in unstable positive feedback and a dangerous
runaway condition in the absence of other changes. The output polarity must be
changed as well to re-establish polarity match for stable negative feedback.