Circuit for performing square root functions

• US 4,734,878 A
• Filed: 10/31/1985
• Issued: 03/29/1988
• Est. Priority Date: 10/31/1985
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Sutcliffe, Patrick L.
• Primary Examiner(s): Harkcom, Gary V.
• Assistant Examiner(s): Mai, Tan V.
• Application Number:
  US06/794,094
• Time in Patent Office: 880 Days
• Field of Search: 364/752, 364/814, 377/39, 377/49
• US Class Current: 708/605
• CPC Class Codes: G06F 7/5525 Roots or inverse roots of single operands

Abstract

Circuitry for computing the square root of a number wherein the input number is partitioned into digit pairs left and right of the radix point. Pairs of zeros are added after the radix point for each digit of the desired precision. The most significant zero digit pairs are skipped to the first digit pair which is not zero, accordingly the first answer bit is a 1. A residue is formed by subtracting the 1 from the digit pair, multiplying by 4, and adding the next most significant digit pair. The procedure is repeated for subsequent bit pairs by defining trial divisors and determining residue values.

Claims

1. Circuitry for performing square root functions comprising

a data register for an input number,

a state counter,

an answer shift register having an input and an output,

a loop including a subtractor having two inputs and an output, a latch connected to said subtractor output and to one of said subtractor inputs, means connecting said subtractor output to said input of said answer shift register, and means connecting said output of said answer shift register to the other of said subtractor inputs,

means connecting data bit pairs stored in said data register to said one of said subtractor inputs, said data bit pairs being selected in response to said state counter and concatenated with data from said latch to form concatenated data as one input to said subtractor from which data from said answer shift register is subtracted, and

said latch receiving an output signal from said subtractor and said answer shift register receiving a "1" bit when said concatenated data is equal to or greater than data from said answer shift register, said latch receiving the concatenated data and said answer shift register receiving a "0" when said concatenated data is less than data from said answer shift register, said loop operating on data until a terminal count is reached by said state counter.

2. Circuitry as defined by claim 1 wherein data from said answer shift register is shifted up two bits before application of said data as an input to said subtractor.

3. Circuitry as defined by claim 1 wherein data pairs from said data register are concatenated as the least significant bits.

4. Circuitry as defined by claim 1 and further including an output buffer connected to receive data from said answer shift register as a square root upon said state counter reaching a terminal count.