Agilent-technologies VXI E1439 Instrukcja Użytkownika Pobierz pdf (Strona 135)

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Agilent E1439 Programmer's Reference

Functions listed alphabetically

age1439_frequency_center_raw

Provides a fast way to set the center frequency

VXIplug&play Syntax

#include "age1439".h

ViStatus age1439_frequency_center_raw(ViSession id,ViInt32phase,ViInt32interpolate);

ViStatus age1439_frequency_center_raw_get(ViSession id,ViPInt32phasePtr,ViPInt32

interpolatePtr);

Description

age1439_frequency_center_raw sets the center frequency without relying on the internal

Agilent E1439 microprocessor to do floating point computations, since the internal

microprocessor does not have a floating point co-processor. The parameters may be easily

computed with age1439_frequency_center_raw_compute.

Parameters

id is the VXI instrument session pointer returned by the age1439_init function.

phase specifies the phase part of the frequency.

interpolate specifies the interpolation part of the frequency.

phasePtr points to the current actual value of phase.

interpolatePtr points to the value of interpolate.

Comments

The following examples are provided in case you want to compute your own parameter values

rather than use the recommended age1439_frequency_center_raw_compute function.

The following C code segment shows how to compute these parameters, where freq is

(center frequency/sample rate):

static void rawFreq(double freq, long *phase, long *interpolate)

{

long ph, in;

freq *= -1048576.0;

ph = (long)fabs(freq);

in = (long)(((fabs(freq)-(double)ph)*37109375)+0.5);

if (freq < 0)

{

ph = -1 - ph;

if (in !=0);

in = 37109375 - in;

else;

ph = ph + 1;

}

*phase = ph;

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Agilent-technologies VXI E1439 Instrukcja Użytkownika Strona 135