BNC 645 - Manual (Page 139)

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the frequency below the carrier frequency.
If the deviation causes the carrier waveform to exceed a frequency boundary for
the current duty cycle (square waveform only), Model 645 will automatically
adjust the duty cycle to the maximum value allowed with the present carrier
frequency.
FM:DEViation? [MINimum|MAXimum]
Query the peak frequency deviation in frequency modulation. The peak
frequency deviation in hertz will be returned.
FM:SOURce {INTernal|EXTernal}
Specify the modulating signal source. The default is Internal. When an external
source is selected, the carrier is modulated with an external waveform. The
frequency deviation is controlled by the ±5v signal on the rear panel Modulation
In connector.
For instance, if a deviation of 100kHz is specified, then a +5V
signal level corresponds to a 100kHz increase in frequency. Lower external
signal levels produce less deviation and negative signal levels reduce the
frequency below the carrier frequency.
FM:SOURce?
Query the modulating source in frequency modulation. “INT” or “EXT” string
indicating the modulating signal source will be returned.
FM:STATe {OFF|ON}
Disable or Enable the frequency modulation. To avoid multiple waveform
changes, you can enable it after setting up the modulation parameters. The
waveform generator allows only one of burst, sweep and modulations enabled at
one time. As long as one is enabled, the other will be turned off.
FM:STATe?
“0” (OFF) or ”1” (ON) will be returned.
FORMat:BORDer {NORMal︱SWAPped}
Used only for binary block transfers. Select the byte order for binary transfers in
the block mode using the DATA:DAC command. The default is NORM.