Reference Manual

Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 226
Note:
If the high/low polarity of the PWM signals is wrong for a particular amplifier,
what was intended to be deadtime between top and bottom on states, as set by
I6m04 becomes overlap. If the amplifier-input circuitry does not lock this out
properly, this causes an effective momentary short circuit between bus power and
ground. This would destroy the power transistors very quickly.
For PFM signals on Output C, non-inverted means that the pulse-on signal is high (direction polarity is
controlled by I7mn8). During a change of direction, the direction bit will change synchronously with the
leading edge of the pulse, which in the non-inverted form is the rising edge. If the drive requires a set-up
time on the direction line before the rising edge of the pulse, the pulse output can be inverted so that the
rising edge is the trailing edge, and the pulse width (established by I6m04) is the set-up time.
For DAC signals on Outputs A and B, non-inverted means that a 1 value to the DAC is high. DACs used
on Delta Tau accessory boards, as well as all other known DACs always expect non-inverted inputs, so
I6mn7 should always be set to 0 or 2 when using DACs on Channel n.
Note:
Changing the high/low polarity of the digital data to the DACs has the effect of
inverting the voltage sense of the DACs’ analog outputs. This changes the polarity
match between output and feedback. If the feedback loop had been stable with
negative feedback, this change would create destabilizing positive feedback,
resulting in a dangerous runaway condition that would only be stopped when the
motor exceeded Ixx11 fatal following error
I7mn8 Servo IC m Channel n PFM Direction Signal Invert Control
Range: 0 - 1
Units: none
Default: 0
I7mn8 controls the polarity of the direction output signal in the pulse-and-direction format for Channel n
of a PMAC2-style Servo IC m. It is only active if I7mn6 has been set to 2 or 3 to use Output C as a
pulse-frequency-modulated (PFM) output. It has the following possible settings:
 I7mn8 = 0: Do not invert direction signal (+ = low; - = high)
 I7mn8 = 1: Invert direction signal (- = low; + = high)
If I7mn8 is set to the default value of 0, a positive direction command provides a low output; if I7mn8 is
set to 1, a positive direction command provides a high output.
I7mn9 Servo IC m Channel n Hardware-1/T Control
Range: 0 – 1
Units: none
Default: 0
I7mn9 controls whether the hardware-1/T functionality is enabled for Channel n of a PMAC2-style Servo
IC m. If I7mn9 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 I7mn9 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 I7mn9 to 1 on an older revision IC
does nothing – software-1/T functions can still be used. However, it is strongly recommended that I7mn9
be left at 0 in this case, to prevent possible problems when copying a configuration to newer hardware.