Arithmetic ? A Special Case
Adders, accumulators, counters, and comparators all depend on carry chains
Carry-chain logic is usually much deeper than the rest of the design
- 32 levels for a 16-bit ripple adder
- too deep to use function generators at 100 MHz
- arithmetic delays would limit performance
Dedicated carry logic provides the desired speed
- 16-bit adders can operate at up to 200?MHz register-to-register