Generating a bit stream in Virtuoso

Hello all,

I want to test a digital chip on Cadence Spectre using its extracted SPICE netlist from Calibre PEX. The chip has a bit stream of 128 bits as input and its outputs are:  a digital bit stream of 128 bits and an analog signal. So what is the best way to generate the input bit stream ?

I found a way using vbit source and loading a bit stream to it using a txt file, but is there a better way ?