Question

5. A binary subtractor can be implemented using the carry look-ahead principle. (a) Draw the truth table of a binary subtractor. Use Xi, Yi, di, bi, and bi+1, for minuend, subtrahend, difference, borrow input, and borrow output respectively. (b) Derive expressions for the borrow-generate Yi and borrow propagate Ti signals for a binary subtractor. (c) Present the design of a circuit to compute d; and bi+1 from Yia Tį, and bi.

Answer 1

@ Borory Subtractors inputs Y; outputs be I biri I X din oooo 01 lo K-map = b; = {(1,2,4,7) x: 00 01, 11,0 O LOLO 1090 fri = Fi y; dint x; v: dönt Xi9; d:, +; v:&: - :0din K-map :- bits = [n(1,2,3,7) = Ty ydion OLD rias trito = 4:+8:9.-9.din) - Bat Fidin +; Y; + Yi din circuit FDTAD Scanned with CamScanner

logical Expression for borrow of;= dönt By dint ydi +xy din = din CXT + xy) thin (Xitoy) .. Edin (XXQubory)+cin (X XOR Y) = din (X.XORY)' + din CX XORY) - din XOR CX XOR Y) CS Cascadin XOR' X XOR V = din cs anne @y