First thing is your question is not elaborate,....,
always@( sensitivity_list),....,which you wrote is used to run always for a change in the reg/wire specified in the sensitivity list.
If you want to run for a repetitive period, then use a clock, which should be mentioned as, always@(posedge clock).
Let me know, if something is confusing. Also, write ur question in detail, if you want to know more about your doubt.
It can be either xmit_ShiftRegH or xmitDataSelH or both. If any of these conditions exist then the statements with in the always block will be executed.