User's Manual

PMAC2 User Manual
Setting Up PMAC2 for Direct PWM Control 17
where n is the PMAC2 channel number. While each channel has its own pins for the clock and strobe
outputs, the signals are actually common for 4 channels (1-4 and 5-8).
PWM/ADC Phase Matching
The current data brought back into PMAC2’s Phase A input must be for the motor phase commanded by
PMAC2’s Phase A PWM output, whatever this phase is called on the motor and drive. The current data
brought back into PMAC2’s Phase B input must be for the motor phase commanded by PMAC2's Phase
B PWM output, whatever this phase is called on the motor and drive.
This may mean that PMAC2’s name for the phase may not match the motor's and drive's name for the
phase. For example, for a motor/drive system that proivides current feedback on Phases A and C,
PMAC2's PWM Phase B outputs would be connected to the drive’s Phase C PWM inputs, the drive's
Phase C current feedback would be connected to PMAC2’s Phase B ADC inputs, and PMAC2’s Phase C
outputs would be connected to the drive’s Phase B PWM inputs.
Amplifier Enable and Fault Interface
There is an amplifier enable/disable output and an amplifier fault input for each motor. Both signals are
differential, for a total of 4 lines: AENAn+, AENAn-, FAULTn+, and FAULTn-. These signals are
almost always part of the amplifier cable and connector.
Supplemental Flags
There are five supplemental flag inputs to PMAC2 for each motor that can be used for several purposes:
T, U, V, W, and USER. The actual signal names are CHTn, CHUn CHVn, CHWn, and USERn. These
are single-ended inputs, pulled up to +5V in the PMAC2.
These flag inputs can be used for low-resolution absolute motor position to prevent the need for a power-
on phasing search on a synchronous motor. The U, V, and W inputs are commonly used for the hall-
effect commutation inputs of a brushless motor. Some motors such as Fanuc have low-resolution binary
absolute tracks on their encoders that can be brought in on T, U, V, and W.
Another use for these flags is as a fault code. T, U, V, and W can serve as a 4-bit fault code to tell PMAC
why the drive faulted.
A third use for these flags is sub-count position information when interpolating from an analog encoder.
PMAC2 can accept up to five bits of fractional information on T, U, V, W, and USER, with T as the most
significant bit, and USER as the least significant bit.
With external multiplexing, it is possible to use these flags for more than one purpose. For example, they
could be used to read hall-effect sensors on power-up, sub-count information in normal operation, and
fault codes when the amplifier has faulted.
Other Signals
If the JMACH connector on PMAC2 connects directly to the amplifier without any interface board, non-
amplifier signals for that motor must be passed through the amplifier, even if they are not used by the
amplifier. This includes , such as encoder, home and limit flags, and hall-effect inputs.
PMAC2 Parameter Setup
Much of the PMAC2 interface hardware is software-configurable through I-variables. This section
provides basic information on each of the I-variables that is important in this type of application. There is
a detailed description of each I-variable in the Software Reference.
Parameters to Set up Global Hardware Signals
PWM Frequency Control: I900, I906
Set PMAC2 I-variable I900 to define the PWM frequency wanted on machine interface channels 1-4
(typically motors 1-4) according to the equation: