Reference Manual

Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 219
The PFM pulse width is specified in PFM_CLK cycles, as defined by I7m03. The equation for I7m04 as
a function of PFM pulse width and PFM_CLK frequency is:
sec)(Width_Pulse_PFM*)MHz(Freq_CLK_PFM04m7I  
+ 1
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
)1047(*2
)(__
)(__


mI
MHzFreqCLKPFM
MHzFreqMaxPFM
For accessory boards in which alternate addressing of the Servo IC is used (labeled Servo IC m*), this
function is controlled by I7m54, not I7m04.
Examples:
A PWM deadtime of approximately 1 microsecond is desired:
I7m04

1 sec / 0.135 sec

7
With a 2.4576 MHz PFM_CLK frequency, a pulse width of 0.4 usec is desired:
I7m04

2.4576 MHz * 0.4 usec

1
See Also: I7m03, I6804
I7m05 Servo IC m DAC Strobe Word
Range: $000000 - $FFFFFF
Units: Serial Data Stream (MSB first, starting on rising edge of phase clock)
Default: $7FFFC0
I7m05 controls the DAC strobe signal for machine interface channels on Servo IC m. The 24-bit word set
by I7m05 is shifted out serially on the DAC_STROB lines, 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.
For a typical n-bit DAC, the strobe line is held high for n-1 clock cycles. Therefore, the common settings
of this variable are:
 18-bit DACs: $7FFFC0 (high for 17 clock cycles)
 16-bit DACs: $7FFF00 (high for 15 clock cycles)
 12-bit DACs: $7FF000 (high for 11 clock cycles)
The default I7m05 value of $7FFFC0 is suitable for the 18-bit DACs on the Acc-8E Analog Interface
Board. I7m05 should not be changed from the default unless different DACs are used.
For accessory boards in which alternate addressing of the Servo IC is used (labeled Servo IC m*), this
function is controlled by I7m55, not I7m05.
I7m06 Servo IC m ADC Strobe Word
Range: $000000 - $FFFFFF
Units: Serial Data Stream (MSB first, starting on rising edge of phase clock)
Default: $FFFFFE
I7m06 controls the ADC strobe signal for machine interface channels on Servo IC m. The 24-bit word set
by I7m06 is shifted out serially on the ADC_STROB lines, MSB first, one bit per ADC_CLK cycle starting
on the rising edge of the phase clock. The value in the LSB is held until the next phase clock cycle.