User's Manual

PMAC User Manual
Setting Up a Motor 61
To PMAC itself, this type of feedback looks like an absolute encoder. The source of the data is the
appropriate timer register, not the Acc-14D I/O register. The $20 or $30 conversion format would be
used, and the data would be found in the Encoder 9 through Encoder 16 timers that measure the time
between the last two pulses (Y:$C020, Y:$C024, ... Y:$C03C). See below under Parallel Position
Feedback Entries for instructions on the software setup for this type of feedback.
For this type of device, PMAC can use the Ix10 parameter to read the absolute power-on/reset position up
to a width of 24 bits. If Ix10 is set to 0, the absolute power-on/reset position read function is disabled,
and the power-on/reset position is set to zero, regardless of the setting of the sensor, and subsequent
position readings are incrementally referenced to this zero position. For more information, refer to the
Absolute Power-Up Position section in this manual, the Ix10 description in the Software Reference
manual, and the Acc-29 MLDT Interface manual.
It is important with this type of feedback device to perform a PMATCH (position-match) function before
the first programmed move after power-up/reset. Usually this is done automatically by having I14 equal
to 1. If this is not done, PMAC will calculate the first move for the motor assuming a starting point of
zero, instead of the true position, leading to unexpected performance on the first move.
Analog Position Feedback
If analog feedback is desired from a potentiometer or an LVDT, PMAC can accept high-band width
analog feedback through one of its analog-to-digital converter boards (Acc-23 or Acc-28). Any
modulated analog position signal must be demodulated before it is presented to the PMAC system so that
a fixed position is represented by a DC voltage. PMAC does not support the software extension of analog
position feedback through its accessory cards, so no rollover should be permitted. Analog feedback
through Acc-23 or Acc-28 requires conversion format $10 (see below).
If the analog data is converted to digital form external to PMAC or its accessory boards, then it will be
fed into PMAC as a parallel data word, and PMAC will treat it like an absolute encoder (see above).
For this type of device, PMAC can use the Ix10 parameter to read the absolute power-on/reset position up
to a width of 16 bits. If Ix10 is set to 0, the absolute power-on/reset position read function is disabled,
and the power-on/reset position is set to zero, regardless of the setting of the sensor, and subsequent
position readings are incrementally referenced to this zero position. For more information, refer to the
Absolute Power-Up Position section in this manual, the Ix10 description in the Software Reference
manual, and the Acc-28 or Acc-36 A/D Converter manual.
With the V1.15 firmware, it is also possible to use the A/D converters on a single Acc-36 for servo-loop
feedback. I60 and I61 are used to specify the address and number of Acc-36 ADC registers to be copied
into RAM automatically during phasing interrupts. The servo loop feedback functions read the data from
these RAM registers, and should treat the data as 12-bit parallel position feedback (see above section).
For this type of device, PMAC can use the Ix10 parameter to read the absolute power-on/reset position up
to a width of 12 bits. If Ix10 is set to 0, the absolute power-on/reset position read function is disabled,
and the power-on/reset position is set to zero, regardless of the setting of the sensor, and subsequent
position readings are incrementally referenced to this zero position.
It is important with this type of feedback device to perform a PMATCH (position-match) function before
the first programmed move after power-up/reset. Usually this is done automatically by having I14 equal
to 1. If this is not done, PMAC will calculate the first move for the motor assuming a starting point of
zero, instead of the true position, leading to unexpected performance on the first move.