The SHIFTERs library consists of the following 4 generic components :
siso : N-bit serial-in / serial-out register
piso : N-bit serial & parallel-in / serial-out register
sispo : N-bit serial-in / serial & parallel-out register
spispo : N-bit serial & parallel-in / serial & parallel-out register
The SHIFTERs library can be verified with this testbench : test_shifters