Maximum Frequency of a 16 Bit RCA
Architects must intuitively understand how datapath width impacts maximum operating frequency before writing any RTL.
The schematic shows a 16-bit Ripple Carry Adder (RCA) constructed from 16 cascaded Full Adder (FA) blocks. Each FA block takes inputs A[i], B[i], and Cin[i], producing outputs Sum[i] and Cout[i]. The primary outputs of the entire 16-bit block are Sum[15:0] and Cout[15].
The delay from any FA input (A, B, or Cin) to the Cout pin is 200 picoseconds (ps). The delay from any FA input to the Sum pin is 250 ps.
Calculate the worst-case propagation delay from the primary inputs to the final outputs. Determine the theoretical maximum operating frequency for this combinational block.
Constraints
- Assume ideal interconnects with zero routing delay between blocks.
- Assume all primary inputs arrive simultaneously at time t = 0.
- Do not account for setup or hold times of external registers.
Topics
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