C-testable carry-free divider

In this paper, the design of a C-testable, high-performance carry-free array divider is presented. A radix-2 redundant number based carry-free divider is considered and modified to make it C-testable, i.e., it can be exhaustively tested using a constant number of test vectors irrespective of its word-length. Previous C-testable designs considered dividers that used carry propagate adders/subtractors. These dividers are slow because of their O(W²) computation time (where W is the word-length of the divider). High-performance carry-free dividers use carry-free redundant arithmetic adders/subtractors. Due to this feature, they have O(W) computation time. The on-the-fly converter used by carry-free dividers to convert the redundant quotient to two's-complement form is shown to be not C-testable. It is modified to be linear-testable (in word-length) instead of exponential time required for exhaustively testing all possible combinations at its inputs. Testing of high-performance carry-free dividers is important and has not been addressed before.