Port(In 1, In 2: in Bit Out 1: out Bit) įor U 0: HA use entity Half_Adder(Behavior_desc) įor U 1: HA use entity Half_Adder(Behavior_desc) įor U 2: OG use entity OR_gate(Behavior_desc) īegin- Connect the ports of the components
Signal Temp_sum, Temp_carry 1, Temp_carry 2: Bit Port(A, B, Carry_in: in Bit Sum, Carry_out: out Bit) Port (In 1, In 2: in Bit Out 1: out Bit) Īrchitecture Behavior_desc of Half_Adder is VHDL description of a half-adder and a full-adder Additionally C o is clocked to the output of the flip-flop and becomes the next C in, while the sum of the two least significant digits is clocked into the left-hand end of R 1 This process is repeated on receipt of each clock pulse ( Ck1) until the two numbers stored initially in R 1 and R 2 have been added and the resulting sum has been clocked back into the register R 1 If at the termination of the addition C o = 1, this will represent the most significant digit of the sum. Ck1 is now used to shift right the digits in registers R 1 and R 2, thus presenting the next most significant pair of digits at terminals A and B. With M = 1, Ck2 is disabled and Ck1 is enabled. The corresponding sum and carry-out appear at the output terminals of the full adder. With M = 0, Ck2 is enabled, the flip-flop is cleared, and the registers are loaded with the two numbers to be added so that the two least significant bits are available at terminals A and B. The selection of either of the two clock pulses is a function of the mode control M (see Figure 12.12). The basic element of the circuit is a full adder which is operated in conjunction with a DFF and a pair of shift registers which have parallel loading and shift right facilities controlled by Ck1 and Ck2. Read more Navigate DownĪ serial adder uses a sequential technique and may be regarded as a very simple finite state machine. Compare delay and size with a 2-bit carry-ripple adder implemented with (radix-2) full-adders (use average delays). 2.3ĭesign a radix-4 full adder using the CMOS family of gates shown in Table 2.4. L load on the gate output * different characteristics for each input + XNOR same characteristics as XOR for full-adder characteristics see Table 2.2 2.2ĭetermine the delay of a 32-bit adder using the full-adder characteristics of Table 2.4 (average delays).
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