Reference Manual
Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 200
I6804/I6854/I6904/I6954 MACRO IC PWM Deadtime / PFM Pulse Width Control
Range: 0 - 255
Units: 16*PWM_CLK cycles / PFM_CLK cycles
PWM Deadtime = [16 / PWM_CLK (MHz)] * I6804 = 0.135 usec * I6804
PFM Pulse Width = [1 / PFM_CLK (MHz)] * I6804
= PFM_CLK_period (usec) * I6804
Default: 15
PWM Deadtime = 0.135 usec * 15 = 2.03 sec
PFM Pulse Width = [1 / 9.8304 MHz] * 15 = 1.526 sec (with default I6803)
Note:
This I-variable is only active if the MACRO IC is present, and a DSPGATE2 IC.
The presence and type of MACRO ICs are reported in I4902 and I4903.
I6804, I6854, I6904, and I6954 control the deadtime period between top and bottom on-times in
PMAC2's automatic PWM generation for the two supplemental machine interface channels of MACRO
ICs 0, 1, 2, and 3, respectively, provided they are DSPGATE2 ICs. In conjunction with I6803 I6853,
I6903, and I6953, they also control the pulse width for PMAC2’s automatic pulse-frequency modulation
generation for the two machine interface channels on the DSPGATE2 MACRO IC.
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 sec. The equation for I6804 (etc.) as a function of PWM deadtime is:
sec135.0
sec)(DeadTime
6804I
The PFM pulse width is specified in PFM_CLK cycles, as defined by I6803 (etc.). The equation for
I6804 (etc.) as a function of PFM pulse width and PFM_CLK frequency is:
sec)(Width_Pulse_PFM*)MHz(Freq_CLK_PFM6804I
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
6804I*2
)MHz(Freq_CLK_PFM
)MHz(Freq_Max_PFM
Examples:
A PWM deadtime of approximately 1 microsecond is desired:
I6804
1 sec / 0.135 sec
7
With a 2.4576 MHz PFM_CLK frequency, a pulse width of 0.4 sec is desired:
I6804
2.4576 MHz * 0.4 sec
1
See Also:
I-variables I6803 (etc.), I7m03, I7m04
I6805/I6855/I6905/I6955 MACRO IC DAC Strobe Word
Range: $000000 - $FFFFFF
Units: Serial Data Stream (MSB first, starting on rising edge of phase clock)
Default: $7FFFC0 (for 18-bit DACs)
Note:
This I-variable is active only if the MACRO IC is present, and is a DSPGATE2 IC.
The presence and type of MACRO ICs are reported in I4902 and I4903.