Customizing libiio-matlab

Hi, I'm trying to go beyond the libiio-matlab example (ad9361_matlab.m, found in MathWorks_tools/hil_models/fmcomms2_3_data_stream) and transmit my own custom waveform. One of the things I noticed while trying to get my code to work is that when I call the stepImpl() function in iio_sys_obj_matlab.m, it passes the data to the writeData() function in libiio_if.m. If I issue a pause command, it will transmit the data multiple times -- it seems like the transmitter will keep looping through the buffer until it is cleared. What do I need to modify if I only want to transmit a single time? Is there any documentation that I can refer to? Thanks for the help!