thanks for your 'little' help. i understand your logic,too. However,the problem here is: I dont know how to describe the 8 bit- two registers in VHDL.
with the first 8 bit register: it has three inputs including cout(1 bit), sum(4 bit),and lower (3 bit ), about the second : 1 input (4 bit sum from the above register) and one ouput(it is the product that we need) One signal between the two registers.. the product includes 4 bit sum, 3 bit-lower, and the last bit is 1.but I still dont know how to write it in vhdl . Can someone else work it out for me? I have added one example , you can see it below.
Hope i will receive nice replying from you^^^
a 0 1 0 1
x 0 1 1 1
----------------------
P(0) 0 0 0 0
+x0.a 0 1 0 1
----------------------
2p(1) 0 0 1 0 1
P(1) 0 0 1 0 1
+x1.a 0 1 0 1
----------------------
2p(2) 0 0 1 1 1 1
P(2) 0 0 1 1 1 1
+x2.a 0 1 0 1
----------------------
2p(3) 0 1 0 0 0 1 1
P(3) 0 1 0 0 0 1 1
+x3.a 0 0 0 0
----------------------
P(4) 0 0 1 0 0 0 1 1
P 0 0 1 0 0 0 1 1