Reference Manual

16-Axis MACRO CPU Software Reference Manual
36 16-Axis MACRO Station MI-Variable Reference
MI904 controls the deadtime period between top and bottom on-times in the 16-Axis MACRO Station’s
automatic PWM generation for machine interface channels 1-4. In conjunction with MI903, it also
controls the pulse width for the 16-Axis MACRO Station's automatic pulse-frequency modulation
generation for machine interface channels 1-4.
The PWM deadtime, which is the delay between the top signal turning off and the bottom signal turning
on, and vice versa, is specified in units of 16 PWM_CLK cycles. This means that the deadtime can be
specified in increments of 0.135 µsec. The equation for MI904 as a function of PWM deadtime is:
MI904 = Deadtime (µsec) / 0.135 µsec
The PFM pulse width is specified in PFM_CLK cycles, as defined by MI903. The equation for MI904 as
a function of PFM pulse width and PFM_CLK frequency is:
MI904 = PFM_CLK Freq (MHz) / PFM pulse width (µsec)
In PFM pulse generation, the minimum off time between pulses is equal to the pulse width. This means
that the maximum PFM output frequency is
PFM Max_Freq (MHz) = PFM_CLK Freq / (2 * MI904)
Examples:
A PWM deadtime of approximately 1 microsecond is desired:
MI904 ≅ 1 µsec / 0.135 µsec ≅ 7
With a 2.4576 MHz PFM_CLK frequency, a pulse width of 0.4 µsec is desired:
MI904 ≅ 2.4576 MHz * 0.4 µsec ≅ 1
See Also:
MI908, MI994
MS{anynode},MI905 DAC 1-4 Strobe Word
Range: $000000 - $FFFFFF
Units: Serial Data Stream (MSB first, starting on rising edge of phase clock)
Default: $7FFF00 (for 16-bit DAC data)
MI905 controls the DAC strobe signal for machine interface channels 1-4. The 24-bit word set by MI905
is shifted out serially on lines DAC_STROB1-4, MSB first, one bit per DAC_CLK cycle starting on the
rising edge of the phase clock. The value in the LSB is held until the next phase clock cycle. ACC-
24E2A backplane analog axis-interface boards have 18-bit DACs; MI905 should be set to $7FFFC0.
See also: MI909, MI999
MS{anynode},MI906 PWM 5-8 Frequency Control
Range: 0 - 32767
Units: PWM Frequency = 117,964.8 kHz / [4*MI906+6]
Default: 6257
PWM Frequency = 117,964.8 / 26114 = 4.5163 kHz
MI906 controls the PWM frequency for machine interface channels 5-8. It does this by setting the limits
of the PWM up-down counter, which increments and decrements at the PWMCLK frequency of
117,964.8 kHz (117.9648 MHz).
The PWM frequency determines the actual switching frequency of amplifiers connected to any of the 16-
Axis MACRO Station's first four machine interface channels with the direct PWM command. The value
of MI906 is only important if the direct PWM command signal format is used on channels 5 to 8.