Reference Manual

PMAC 2 Software Reference
PMAC I-Variable Specification 109
Ix79 Motor x Second Phase Offset
Range
-32,768 .. 32,767
Units
16-bit DAC/ADC bit equivalent
Default
0
Remarks
Ix79 serves as an output or feedback offset for Motor x; its exact use depends on the mode of
operation as described below:
Mode 1: When PMAC is not commutating Motor x (Ix01 = 0) and the output is bipolar (Ix02
bit 16 = 1, the default), Ix79 is not used. Ix29 is the offset for this mode.
Mode 2: When PMAC is not commutating Motor x (Ix01 bit 0 = 0) but is in sign-and-
magnitude output mode (Ix02 bit 16 = 1 – PMAC(1) only), Ix79 is the offset of the command
output value after the absolute value is taken (Ix29 is the offset before the absolute value is
taken). Ix79 is typically used in this mode to compensate for analog offsets in interface
circuitry, either in DACs or in voltage-to-frequency converters.
Mode 3: When PMAC is commutating Motor x (Ix01 = 1) but not closing the current loop
(Ix82 = 0), Ix79 serves as the offset for the second of two phase command output values (Phase
B), for the address specified by Ix02 plus 1; Ix29 serves the same purpose for the first phase.
Ix79 is added to the output command value before it is written to the command output register.
When commutating from a PMAC(1), Phase A is output on the higher-numbered of the two
DACs (e.g. DAC2), Phase B on the lower-numbered (e.g. DAC1). When commutating from a
PMAC2, Phase A is output on the A-channel DAC (e.g. DAC1A), Phase B on the B-channel
DAC (e.g. DAC1B).
As an output command offset, Ix79 is always in units of a 16-bit register, even if the actual
output device is of a different resolution. For example, if a value of 60 had to be written into an
18-bit DAC to create a true zero command, this would be equivalent to a value of 60/4=15 in a
16-bit DAC, so Ix79 would be set to 15 to cancel the offset.
Mode 4: When PMAC is commutating (Ix01 = 1) and closing the current loop for Motor x
(Ix82 > 0), Ix79 serves as an offset that is added to the phase current reading from the ADC for
the second phase (Phase B), at the address specified by Ix82. Ix29 performs the same function
for the first phase. The sum of the ADC reading and Ix79 is used in the digital current loop
algorithms.
As an input feedback offset, Ix79 is always in units of a 16-bit ADC, even if the actual ADC is
of a different resolution. For example, if a 12-bit ADC reported a value of -5 when no current
was flowing in the phase, this would be equivalent to a value of -5*16=-80 in a 16-bit ADC, so
Ix79 would be set to 80 to compensate for this offset.
Ix80 Motor x Power-Up Mode
Range
0 .. 7
Units
None
Default
0
Remarks
Ix80 controls the power-up mode, including the phasing search method (if used), for Motor x.
It consists of 3 independent control bits, each determining one aspect of the state of the motor at
power-up or full board reset:
• Bit 0 controls whether the motor is enabled at power-up/reset or not. If bit 0 is set to 0, the
motor is left in the “killed” (disabled) state at power-up/reset, and a command must be
issued to the motor to enable it. If bit 0 is set to 1, the motor is automatically enabled at
power-up/reset, and if a phasing search move is required to establish the commutation
position reference, this is automatically done.