There are several ways to tackle this problem (that I can think of). One of the ways is to use spectre's ability to define patterns (see "spectre -h pattern"). If I create a file called (say) "patterns.scs" and include it in ADE as a model library:
// my patterns
p1 pattern data="10111011011"
p2 pattern data="001100100101011"
p3 pattern data="1111100001110001100"
Then on the vbit source (or vsource with type set to "bit"), I can set the pattern as (say) "p1,p2,p3" or "p1,p2,p2,p3,p1" - whatever you like - and it will then use the sequence of predefined patterns from the include file.
The alternative is to use the "vector" file input. Look at Setup->Simulation Files and there's a Vector Files tab. You can add the path to vector files. For more details on the syntax, look at "spectre -h vector". The precise details of the format are in the Ultrasim User Guide (<MMSIMinstDir>/doc/UltraSim_Use/UltraSim_User.pdf) - in the chapter entitled "Digital Vector File Format"). This allows you to take a file of vectors (in different radixes) and connect to one or more signals in your circuit - replacing the need for sources on the schematic.