Abstract: A method and apparatus for a multi-purpose adder is described. The method includes calculation of an initial sum for each corresponding N-bit portion of a received addend signal and a received augend signal. Generation of an initial carryout signal for each calculated initial sum is then performed. Next, an intermediate sum for each group of M-initial sums according to a respective initial carryout value of each initial sum is then generated. Once generated, an intermediate carryout value for each generated intermediate sum is then calculated. Finally, a final sum is calculated from the intermediate sums generated according to a respective intermediate carryout of each intermediate sum.

Abstract: In one embodiment of the present invention, a high-speed adder is provided. This adder may incorporate a conversion circuit in a slack propagation timing path to provide for improved performance. The present invention may be incorporated into single or multi-bit adders.

Abstract: In association with a circuit for adding binary numbers, it is often useful to increment the sum by a value of 1, for example on a conditional basis. Each of the combined adder and incrementer circuits embodying the invention also provides an output indicating whether a CarryOut signal resulted from the incrementing operation, or whether the CarryOut signal resulted from the addition. The preferred embodiments utilize prefix-type adder circuits using a single carry chain. Alternate embodiments generate a CarryOut signal as a function of the incrementing operation, using either generate and propagate signals or from generate and kill signals from the carry chain.

Abstract: An n-bit prefix tree adder includes n prefix trees, each associated with a bit position of the adder and including a number of computation stages. The computation stages for each of the bit positions include a sum computation stage implemented in logic circuitry. For a subset of the bit positions, the corresponding sum computation logic circuitry computes a sum based at least in part on group-generate, group-transmit and intermediate carry signals. Advantageously, the sum computation logic circuitry is configured to exploit differences in delay associated with generation of the group-generate, group-transmit and intermediate carry signals, so as to reduce the total computational delay of the adder.

Abstract: A circuit which first shifts both a dividend and a divisor by an extra bit such that a 1-bit shift can be avoided after subtraction of the shifted values of dividend and the divisor, while performing a conditional subtraction instruction. The shifted divisor can conveniently replace the dividend as required for the instruction. The approach can be used to implement, among others, 2N-bit/N-bit (denoted 2N/N) division using an N-bit ALU, N/N division using N-bit ALU. The division can be implemented for all possible values of N without requiring substantially more complexity in the implementation.

Abstract: A carry-ripple adder contains 4 or 3 first inputs for receiving 4 or 3 input bits which have the same significance w and are to be summed, and 2 second inputs for receiving two carry bits with the significance w. In addition, the adder contains an output for a sum bit with the significance w and two outputs for two carry bits with the significances 2w and 4w.

Abstract: A circuit and method for deriving an adder output bit from adder input bits, a multiplier circuit, a method of multiplying, a microprocessor and digital signal processor (DSP) employing the circuit or the method and a method of selecting weights and thresholds for logic gates. In one embodiment, the circuit includes: (1) first, second and third logic gates that generate intermediate bits based on threshold comparisons of concatenations of ones of the adder input bits and (2) combinatorial logic that generates the adder output bit from the intermediate bits. In one embodiment, the multiplier includes a summer having at least two inputs with corresponding weights, the inputs corresponding to bits of a multiplicand, the weights based on a multiplier, the summer generating a weighted sum of the multiplicand that represents a multiplication of the multiplicand and the multiplier that is a function of the weighted sum.

Abstract: A circuit and method for deriving an adder output bit from adder input bits, a multiplier circuit, a method of multiplying, a microprocessor and digital signal processor (DSP) employing the circuit or the method and a method of selecting weights and thresholds for logic gates. In one embodiment, the circuit includes: (1) first, second and third logic gates that generate intermediate bits based on threshold comparisons of concatenations of ones of the adder input bits and (2) combinatorial logic that generates the adder output bit from the intermediate bits. In one embodiment, the multiplier includes a summer having at least two inputs with corresponding weights, the inputs corresponding to bits of a multiplicand, the weights based on a multiplier, the summer generating a weighted sum of the multiplicand that represents a multiplication of the multiplicand and the multiplier that is a function of the weighted sum.

Abstract: An adder circuit is provided that generates the sum and sum complement (sum_) signals by constructing the logic in such a way that various levels of both N-type devices and P-type devices are both “on” at the same when that leg is to be open. The logic is then determined by another level and only one P or N type device is one at a given time. For carry and carry complement (carry_) signals a circuit is provided that is symmetrical with respect to P and N devices. The carry and carry— signals are generated by inputting the complement signals to the same circuit used to generate the carry signal. The symmetrical P and N type devices are complementary in that associated devices are on or off with respect to each other. Both the carry and carry— signals are concurrently output. The symmetric nature of the static, dual rail, simultaneous, sum and carry circuits will improve switching performance and minimize the floating body effect that can be found in silicon on insulator (SOI) devices.

Abstract: Each binary carry logic circuit 20 of half adder circuits other than that for the least significant digit comprises a transfer gate 212 turned on when an input bit A2 is active and receiving a carry-in bit *C2 at its data input, and a transistor 23, turned on when the input bit A2 is inactive, connected between a power supply potential VDD and the data output of the transfer gate 212 a signal on which is a carry-out bit *C3. Transfer gates 212 to 214 of binary carry logic circuits other than that for the least significant digit are connected in chain, and are simultaneously on/off controlled by input bits A2 to A4, letting the carry-in bit *C2 from the least significant digit propagate through the transfer gate chain at a high speed.

Abstract: A power saving device and method for either adding or subtracting a constant from an operand, by checking a logic value of a portion of the operand and deciding whether to activate a multi-bit adder or to perform the subtraction or addition by inverting a portion of the operand. The power saving device and method is especially efficient when the constant K equals 2n. Then, the n'th bit of the operand is checked and if the addition or subtraction operation can be performed by inverting the n'th bit of the operand, a result is generated by that inversion, while a multi-bit adder is disabled.

Abstract: The sum interval detector has two n-bit inputs, a 1-bit carry input, and a 1-bit output, which is activated when the sum of the input values lies within the interval −2p . . . 2p−1 or the like. The circuit utilizes a known method to detect whether a sum is equal to a constant to detect whether the upper n−p bits of the sum are binary 000 . . . 0, i.e. 0, or binary 111 . . . 1, i.e. −1, while the lower p bits of the sum are ignored corresponding to XXX . . . X. The method requires that the carry at position p be known which occurs with a well known, fast carry look-ahead circuit. By adding inverters and two levels of full adders the sum interval detector is capable of deciding whether two effective addresses, which each is a sum of base address plus offset, are so close, that the associated data areas overlap.

Abstract: The inventive adder can perform carry look-ahead calculations for a bi-endian adder in a cache memory system. The adder can add one of +/−1, 4, 8, or 16 to a loaded value from memory, and the operation can be a 4 or 8 byte add. The inventive adder comprises a plurality of byte adder cells and carry look-ahead (CLA) logic. The adder cells determine which of themselves is the least significant bit (LSB) byte adder cell. The LSB cell then adds one of the increment values to its loaded value. The other cells add 0x00 or 0xFF, depending upon the sign of the increment value, to a loaded value from memory. Each adder performs two adds, one for a carry-in of 0, and the other for a carry in of 1. Both results are sent to a MUX. The CLA logic determines each of the carries, and provides a selection control signal to each MUX. of the different cells.

Abstract: An adder for adding a signal at a first input (A) and a second input (B) to produce an adder output (S) is disclosed. The adder comprises a bypass input (bypass) and a logic circuit, communicatively coupled to the bypass input (bypass), the first input (A), and the second input (B), the logic circuit configured to hold at least one of the first input (A) and the second input (B) according to the bypass input (bypass).

Abstract: According to the invention, a processing core is disclosed that includes a first source register, a number of second operands, a destination register, and a number of arithmetic processors. A bitwise inverter is coupled to at least one of the first number of operands and the second number of operands. The first source register includes a plurality of first operands and the destination register includes a plurality of results. The number of arithmetic processors are respectively coupled to the first operands, second operands and results, wherein each arithmetic processor computes one of a sum and a difference of the first operand and a respective second operand.

Abstract: A one's complement adder uses two two's complement adders, both of which are coupled to receive first and second addends at their addend inputs, however the first two's complement adder is adapted to output a first sum that is the one's complement sum that would result if no carry occurred upon addition of the first and second addends and the second two's complement adder is adapted to output a second sum that is the one's complement sum that would result if a carry did occur. A selector selects one of the first sum and the second sum as its output (and the output of the one's complement adder) based on whether or not a carry occurred.

Abstract: A family of embodiments of a new class of CMOS VLSI computer multiplier circuits that are simpler to fabricate, smaller, faster, more efficient in their use of power, and easier to scale in size than the prior art. The normal binary adder circuit unit is replaced by the innovative shift switch circuit unit. Use of the shift switch circuit sharply reduces fluctuations of power caused by plurality variations in the bit representations of the input, intermediate and output numbers. Reduced-scale devices are used in shift-switch pass-transistor signal restoration circuits, significantly reducing the size, power demand, and power dissipation of internal circuitry, in contrast to ordinary multiplier design. The simplicity of the circuit design allows multiplier partial-product reduction in fewer logic stages than existing comparable designs allow, showing speed improvement over such designs.

Abstract: The process for performing operations with a variable arithmetic does not call for any shifting of the data in the different registers that come into play in the operation. The input registers can have empty parts which are completed by appropriate bit sequences to ensure a propagation of a possible outgoing carry over in order to recover that carry over from a result register.

Abstract: A circuit and method for deriving an adder output bit from adder input bits, a multiplier circuit, a method of multiplying, a microprocessor and digital signal processor (DSP) employing the circuit or the method and a method of selecting weights and thresholds for logic gates. In one embodiment, the circuit includes: (1) first, second and third logic gates that generate intermediate bits based on threshold comparisons of concatenations of ones of the adder input bits and (2) combinatorial logic that generates the adder output bit from the intermediate bits. In one embodiment, the multiplier includes a summer having at least two inputs with corresponding weights, the inputs corresponding to bits of a multiplicand, the weights based on a multiplier, the summer generating a weighted sum of the multiplicand that represents a multiplication of the multiplicand and the multiplier that is a function of the weighted sum.

Abstract: A circuit and method for deriving an adder output bit from adder input bits, a multiplier circuit, a method of multiplying, a microprocessor and digital signal processor (DSP) employing the circuit or the method and a method of selecting weights and thresholds for logic gates. In one embodiment, the circuit includes: (1) first, second and third logic gates that generate intermediate bits based on threshold comparisons of concatenations of ones of the adder input bits and (2) combinatorial logic that generates the adder output bit from the intermediate bits. In one embodiment, the multiplier includes a summer having at least two inputs with corresponding weights, the inputs corresponding to bits of a multiplicand, the weights based on a multiplier, the summer generating a weighted sum of the multiplicand that represents a multiplication of the multiplicand and the multiplier that is a function of the weighted sum.

Abstract: A method and an apparatus for controlling calculation error produced by the accumulation error due to digit truncation in a non-integer computation. The error is eliminated by controlling the values of LSB, C.sub.in and the addition/subtraction selecting signal as, so that C.sub.in is not necessarily equal to C.sub.in. Considering a even number of cascaded pipelines, C.sub.in in the odd pipelines is set as 0, wherein C.sub.in in the even pipelines is set as 1. The resultant error is thus eliminated mutually by odd and even pipelines.

Abstract: An adder (300) generates encoded outputs to conserve power. In particular, the adder provides "B2" encoded outputs which only drive one bit per every two bits at a time on conductive lines in a data processing system. A binary input is encoded by an encoder (800, 304) to generate a plurality of bits. The plurality of bits are concatenated to form a plurality of sum values. A portion of the plurality of sum values are then selectively output in response to a logic value of a carry kill signal, a carry generate signal, and a carry propagate signal.

Abstract: A circuiting method is disclosed for adding operands of multiple size. This circuit and method employ an n bit adder having n first and second inputs. A first m bit operand is inputted into the m least significant first inputs of the adder, where n is greater than m. A second m bit operand is inputted into the m least significant circuit inputs of the adder. A first (n-m) bit operand is inputted into the (n-m) most significant first inputs of the adder. Each bit of the first (n-m) bit operand represents logical 0. A second (n-m) bit operand is inputted into the most significant (n-m) second inputs of the adder. Each bit of the second (n-m) bit operand represents a logical 1. The first and second m bit operands, the first and second (n-m) bit operands and a carry in bit provided to a carry input node of the adder, are all inputted in parallel. In response, the adder generates n carry bits and n bit output operand.

Abstract: The expression A-sign(A), where A is a signed binary integer represented in 2's complement form, sign(A) is equal to one when A is greater than zero, sign(A) is equal to zero when A is zero, and sign(A) is equal to negative one when A is less than zero, is calculated by bit-complementing A, bit-complementing (A-1) when A is less than zero, bit-complementing A when A is equal to zero, and bit-complementing (A+1) when A is greater than zero. Zero detect for A is provided by determining whether a first carry-out bit from (A+0) and a second carry-out bit from (A+1) have different logical values. In this manner, A-sign(A) can be calculated by a general purpose computer in a single instruction cycle.

Abstract: A binary adder circuit includes carry evaluation circuits that encode a carry production control signal using two signal values (V, W) such that V=W=0 indicates a carry kill, V=W=1 indicates a carry generate and V.noteq.W indicates a carry propagate. The carry evaluation circuit may be implemented in static or dynamic CMOS logic.

Abstract: A rectifying transfer gate circuit includes first and second field effect transistors and one diode. The source of the first field effect transistor is coupled to a first input node and the gate thereof is coupled to a second input node. Meanwhile, the source of the second field effect transistor is coupled to the second input node and the gate thereof is coupled to the first input node. The diode is coupled between the common drain of the first and second field effect transistors and an output node, so as to increase the speed of the operation in the application circuit utilizing the above rectifying transfer gate circuit.