Reference Manual

Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 209
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
I6804 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 I68n8). 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 I6804) 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
I68n7 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
Note:
By default, only the C outputs (PWM or PFM) of MACRO IC 0 are used on a
Turbo PMAC2. The A and B outputs are the alternate use of pins on the I/O port.
I68n8/I69n8 MACRO IC Channel n* PFM Direction Signal Invert Control
Range: 0 - 1
Units: none
Default: 0
Note:
This I-variable is only active if the MACRO IC is present, and is a “DSPGATE2”
IC. The presence and type of MACRO ICs are reported in I4902 and I4903.
I68n8 and I69n8 control the polarity of the direction output signal in the pulse-and-direction format for
machine interface channel n* (n* = 1 to 2) on a “DSPGATE2” MACRO IC. For MACRO ICs 0 and 2, n
= n*; for MACRO ICs 1 and 3, n = n* + 5 (i.e. I6818 controls MACRO IC 0 Channel 1; I6978 controls
MACRO IC 3 Channel 2). They have the following possible settings:
 I68n8/I69n8 = 0: Do not invert direction signal (+ = low; - = high)
 I68n8/I69n8 = 1: Invert direction signal (- = low; + = high)
If I68n8/I69n8 is set to the default value of 0, a positive direction command provides a low output; if
I68n8/I69n8 is set to 1, a positive direction command provides a high output.
I68n9/I69n9 Reserved for Future Use