Comments on Low-energy CSMT carry generators and binary adders

In the above-naed article [ibid., vol. 7, no. 4, pp. 450¿462, Dec. 1999], the author has presented a multiplexer-based carry-select modified tree (CSMT) adder design. It was correctly pointed out in Section VI that these multiplexer-based adders are not just limited to redundant-to-binary-conversion- based adders, but can also be used in the context of carry-save binary adders. However, the carry-update recursion, based on p and g signals, given by [1, eq. (9)] cannot be used to exploit the CSMT adder principles in the above-named article. Here p and g, respectively, represent carry-propagate and carry-generate signals. This letter presents the correct carry-update recursion.