Page 533 - Introduction to Information Optics

518 9. Computing with Optics

XM Xi ; fi X>i 5 T irl V & ij V
i i 1 , i 1 i 1
-r*l
Reference Reference Reference Reference
Digit Digit Digit Digit
Gen ereitor Generalor Generator Generator
£ X^i
! . 1 1
Intermeiiate Intermediate Interme ciiate
Carry and Sum Carry and Sum Carry ancI Sum
Generator Generator Generator
. 1 4 %l l
Pwl *.| ft H t •T,
Final Sum r Final Sum
Generator Generator
1 |

Fig. 9.19. Diagram of the three-step digit-set restricted MSD adder/subtractor [144].

in the following example:
(X) 0T01TT011 =(-117) 10
(Y) ^11001101 =(69)j 0
step l:(R) 001000110
step 2: (C) OOOTIOOOO^
(S) 0000110000

step 3: (Z) OOOlOlOOOO = (-48) 10.

Here the symbol 0 denotes a padded zero.

Table 9.17
Reduced Truth Table for the Three-Step Digit-Set-Restricted MSD Addition with
Nonrestricted Reference Digits [144]

Step Output Output Input
order function literal function Minterms

Step 1 r n-i T xtfi TT
l Id 01 ,01
Step 2 <••,•+! T x,. y,r t d T,00, Od TlO, ddl
.S, 1 d TlOO, Od T,0, OOd,,, dudiidn
Step 3 z { T CiS, TO
l 01