Delta Tau GEO MACRO DRIVE User Manual download pdf (Page 169)

Geo MACRO Drive User and Reference Manual

Geo Macro Drive MI-Variable Reference 157

SCLK Divider N: 5

PFM_CLK Divider N: 4

DAC_CLK Divider N: 3

ADC_CLK Divider N: 4

MI993 = 5 + (8 * 4) + (64 * 3) + (512 * 4) = 5 + 32 + 192 + 2048 = 2277

MI993 has been set to 3429. What clock frequencies does this set?

N1 = INT (3429/512) = 6 ADC_CLK = 611.44 kHz

MI993' = 3429 - (512*6) = 357

N2 = INT (357/64) = 5 DAC_CLK = 1.2288 MHz

MI993'' = 357 - (64*5) = 37

N3 = INT (37/8) = 4 PFM_CLK = 2.4576 MHz

N4 = 37 - (8*4) = 5 SCLK = 1.2288 MHz

MS{node},MI994 PWM Deadtime

Range: 0 - 255

Units: PWM Deadtime = [16 / PWM_CLK (MHz)] * MI994 = 0.135 µsec * MI994

PFM Pulse Width = [1 / PFM_CLK (MHz)] * MI994

= PFM_CLK_period (µsec) * MI994

Default: 15

PWM Deadtime = 0.135 µsec * 15 = 2.03 µsec

PFM Pulse Width = [1 / 9.8304 MHz] * 15 = 1.526 µsec (with default MI993)

MI994 controls the deadtime period between top and bottom on-times in the Geo MACRO Station’s

automatic PWM generation for machine interface handwheel channels 19 and 2. In conjunction with

MI993, it also controls the pulse width for PMAC2’s automatic pulse-frequency modulation generation

for these machine interface channels.

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 MI994 as a function of PWM deadtime is:

MI994 = Deadtime (µsec) / 0.135 µsec

The PFM pulse width is specified in PFM_CLK cycles, as defined by MI993. The equation for MI994 as

a function of PFM pulse width and PFM_CLK frequency is:

MI994 = 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 * MI994)

Examples:

A PWM deadtime of approximately 1 microsecond is desired:

MI994 ≅ 1 µsec / 0.135 µsec ≅ 7

With a 2.4576 MHz PFM_CLK frequency, a pulse width of 0.4 µsec is desired:

MI994 ≅ 2.4576 MHz * 0.4 µsec ≅ 1

MS{node},MI995 MACRO Ring Configuration/Status

Range: $0000 - $FFFF (0 - 65,535)

Units: none

Default: $0080

1 2 ... 164 165 166 167 168 169 170 171 172 173 174 ... 204 205

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Delta Tau GEO MACRO DRIVE User Manual Page 169

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