VXI VT1538A user manual Variable Width Pulse Train PWM

Variable Width Pulse Train (PWM)

This means that the E1538 outputs a continuous train of pulses whose logic 1 pulse width is controlled by the algorithm. The frequency is set by a SCPI command before INIT. Use the following command sequence to set up this mode:

SOURce:FUNCtion:PULSe (@<ch_list>) to enable pulse generation. SOURce:PULM[:STATe] ON,(@<ch_list>) to select the PWM mode SOURce:PULSe:PERiod <period>,(@<ch_list>) to set the pulse repetition period (frequency = 1/<period>). <period> can range from 25μSec to 7.812mSec.

The pulse width value sent by the algorithm can range from 7.87μSec to <period>-7.87μSec. Resolution within this range is 238.4nSec.100% duty-cycle is output when the algorithm sends a value greater than or equal to <period>. 0% duty-cycle is output when the algorithm sends a value less than or equal to 0.

To configure channel 45 to output a variable pulse width continuous train

SOUR:FUNC:PULS (@145)	channel sources pulses...
SOUR:PULM ON,(@145)	and continuous PWM train
SOUR:PULS:PER .0005,(@145)	.5 msec period (2KHz freq)

The algorithm can now output a value to channel 45 to control pulse width of the logic 1 portion of the waveform:

O145 = 333E-6 /* channel 45 pulse width will be 333 μsec */

Figure 17. Output Pulse-Width-Modulated Signal

26 Agilent E1538A Enhanced Frequency/Totalize/PWM SCP