Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
Setting Up Feedback and Master Position Sensors
65
or:
)
kHz
(
Freq
_
PFMCLK
)
kHz
(
OutputFreq
*
216
,
777
,
16
926
MI
=
To produce a pulse output frequency of 1.667 kHz with the default PFMCLK frequency of 9.83 MHz, we
calculate:
calculate:
982
,
2
830
,
9
667
.
1
*
216
,
777
,
16
926
MI
=
=
Note:
The servo update time for the motor using the MLDT should be at least as high as
the output time set here (the servo frequency should be as low as or lower than the
output frequency).
the output time set here (the servo frequency should be as low as or lower than the
output frequency).
PFM Pulse Width: I7m04, I6804, MI904, MI908, MI994
The width of the output pulse is controlled by the PFMCLK frequency with I7m04 for the channels on
Servo IC m, I6804 for the channels on MACRO IC 0, or MI904, MI908, or MI994 for the ICs on a
MACRO Station. This I-variable specifies the pulse width as the number of PFMCLK cycles. At the
default PFMCLK frequency of 9.83 MHz, the default value of 15 produces a 1.5-
Servo IC m, I6804 for the channels on MACRO IC 0, or MI904, MI908, or MI994 for the ICs on a
MACRO Station. This I-variable specifies the pulse width as the number of PFMCLK cycles. At the
default PFMCLK frequency of 9.83 MHz, the default value of 15 produces a 1.5-
µsec output pulse width.
This should be satisfactory for most MLDT devices. When using the RPM format or equivalent (see
Signal Format, above), the pulse width must be large enough to enclose the rising edge of the returned
start pulse – that is, it must be longer than the delay between the output pulse and the returned start pulse.
Signal Format, above), the pulse width must be large enough to enclose the rising edge of the returned
start pulse – that is, it must be longer than the delay between the output pulse and the returned start pulse.
PFM Format Select: I7mn6, I68n6, MI916
The output format of channel signals is controlled by variable I7mn6 for Servo IC m Channel n, by I68n6
for MACRO IC 0 Channel n, or by node-specific variable MI916 on a MACRO Station. In order for the
C-register circuitry of Channel n to output a PFM pulse train rather than a PWM pulse train, this variable
must be set to 2 or 3. Most commonly, it will be set to 3, so that the A and B registers for Channel n
output DAC signals rather than PWM.
for MACRO IC 0 Channel n, or by node-specific variable MI916 on a MACRO Station. In order for the
C-register circuitry of Channel n to output a PFM pulse train rather than a PWM pulse train, this variable
must be set to 2 or 3. Most commonly, it will be set to 3, so that the A and B registers for Channel n
output DAC signals rather than PWM.
Note:
One channel of Turbo PMAC cannot be used simultaneously for direct PWM
control of a motor and for MLDT pulse generation. Direct PWM control of a
motor writes to the channel’s A, B, and C registers every phase cycle
automatically.
control of a motor and for MLDT pulse generation. Direct PWM control of a
motor writes to the channel’s A, B, and C registers every phase cycle
automatically.
MLDT Feedback Select: I7mn0, I68n0, MI910
The decoding of the signals on the encoder inputs is controlled by I7mn0 for Servo IC m Channel n, I68n0
for MACRO IC 0 Channel n, or by node-specific variable MI910 for a channel on a MACRO Station. For
proper decoding of the MLDT signal, this variable must be set to 12. With this setting, the pulse timer is
cleared to zero at the falling edge of the output pulse. It then counts up at 117.96 MHz until a rising edge on
the return pulse is received, at which time the timer’s value is latched into a memory-mapped register that
the processor can read. This register is the X-register at the base address of each channel.
for MACRO IC 0 Channel n, or by node-specific variable MI910 for a channel on a MACRO Station. For
proper decoding of the MLDT signal, this variable must be set to 12. With this setting, the pulse timer is
cleared to zero at the falling edge of the output pulse. It then counts up at 117.96 MHz until a rising edge on
the return pulse is received, at which time the timer’s value is latched into a memory-mapped register that
the processor can read. This register is the X-register at the base address of each channel.
Note:
The MLDT feedback uses the same circuitry that would be used for quadrature
encoder feedback on that channel, so an encoder and MLDT cannot be connected
simultaneously to the same channel’s feedback on Turbo PMAC. In this mode, it
is the pulse timer that is used as a position measurement for feedback, not the pulse
counter that is used with encoders. The counter still registers the number of pulses
returned, but does not represent a position measurement here.
encoder feedback on that channel, so an encoder and MLDT cannot be connected
simultaneously to the same channel’s feedback on Turbo PMAC. In this mode, it
is the pulse timer that is used as a position measurement for feedback, not the pulse
counter that is used with encoders. The counter still registers the number of pulses
returned, but does not represent a position measurement here.