Ok thanks very much for the picture, perfect thanks!
But i'm still not clear about the shift register,
I thought a 4 bit shift register with 4 functions to perform required 4 dq flip flops, and each one preceded by 1 of the 4 multiplexers.. with each of those 4 inputs being fed from different points in the circuit (depending on the functionality).
I mean, otherwise where is the common clock?
Sorry I should have mentioned that there were 4 functions required (if it made a difference):
00: No change
01: Artithmetic shift right
10: Shift Left Carry Out
11: Shift Left Carry In
Thanks for any clarification