Clamping divider, processor having clamping divider, and method for clamping in division

• US 5,928,318 A
• Filed: 09/05/1997
• Issued: 07/27/1999
• Est. Priority Date: 09/09/1996
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Araki, Yoshitsugu
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): Lee, Douglas S.
• Application Number:
  US08/923,926
• Time in Patent Office: 690 Days
• Field of Search: 364/736.01, 364/745.01, 364/745.03, 364/745.02, 364/748.04, 364/748.1, 364/737, 364/761-765
• US Class Current: 708/650
• CPC Class Codes: G06F 7/49921 Saturation, i.e. clipping the result to a minimum or maximum value
• CPC Class Codes: G06F 7/535 Dividing only

Abstract

A clamping divider has a bit shifter, a multiple accumulator (MAC), and an output circuit. When executing a division with the use of a clamp value of 2^m, the bit shifter shifts one of the divisor and dividend of the division, and the MAC subtracts the shifted one from the other to determine, before calculating a quotient of the division, whether or not a result of the division must be clamped.

Claims

1. A clamping divider to be formed in a pipeline processor operating with a sequence of cycles, for clamping a result of a division to a maximum clamp value of 2^m (m being an integer) if a quotient of the division is determined to become equal to or larger than the maximum clamp value and to a minimum claim value of 2ⁿ (n being an integer) if the quotient is determined to become equal to or smaller than the minimum clamp value, comprising:

(a) a bit shifter for shiftings at a one of cycles in the sequence of the cycles, a divisor or a dividend of the division in a higher or lower direction by m bits, and shifting, at another one of cycles in the sequence of the cycles, the divisor or the dividend in a higher or lower direction by n bits;

(b) a multiple accumulator (MAC) for subtracting the dividend or divisor shifted by the bit shifter from the divisor or dividend, and according to a result of the subtraction, determining at the one cycle whether or not the result of the division must be clamped to the maximum clamp value before calculating the quotient, determining at the another one cycle whether or not the result of the division must be clamped to the minimum clamp value before calculating the quotient, and calculating the quotient at a cycle after the one and another one cycles; and

(c) an output circuit for providing the result of the division according to the determination made by the MAC.

2. The clamping divider of claim 1, further comprising a priority encoder for receiving a divisor for standardizing the divisor to a value and an input barrel shifter for receiving the output of the priority encoder, the divisor and a dividend,

wherein the maximum clamp value is set to "1" or below, the dividend and the divisor are shifted by the input barrel shifter, and the MAC multiplies the shifted dividend by a reciprocal of the divisor to determine the quotient.

3. The clamping divider of claim 1, wherein the MAC has a multiplier and an adder/subtracter.

4. The clamping divider of claim 2, wherein the MAC has a multiplier and an adder/subtracter.

5. A clamping divider for clamping a result of a division to a maximum clamp value of 2^m (m being an integer) if a quotient of the division is equal to or larger than the maximum clamp value and to a minimum clamp value of 2ⁿ (n being an integer) if the quotient is equal to or smaller than the minimum clamp value, comprising:

(a) a bit shifter for shifting a divisor or a dividend of the division in a higher or lower direction by m bits when determining whether or not the quotient is equal to or greater than the maximum clamp value, and in a higher or lower direction by n bits when determining whether or not the quotient is equal to or smaller than the minimum clamp value;

(b) a multiple accumulator (MAC) for subtracting the dividend or divisor shifted by the bit shifter from the divisor or dividend and according to a result of the subtraction, before calculating the quotient, determining whether or not the result of the division must be clamped to the maximum or minimum clamp value; and

(c) an output circuit for providing the result of the division according to the determination made by the MAC, wherein the output circuit comprises;

a 3-input selector for receiving the output of the MAC and the maximum and minimum clamp values; and

an output register for holding the output of the selector.

7. The clamping divider of claim 5, further comprising an output barrel shifter connected to the output register.

8. The clamping divider of claim 5, further comprising:

a priority encoder for receiving the divisor;

an input barrel shifter for receiving the output of the priority encoder as well as the divisor; and

a ROM for receiving the output of the input barrel shifter through a register, wherein;

the output of the ROM is supplied to the MAC through a register and a selector.

17. The clamping divider of claim 5, wherein the MAC has a multiplier, a 2-input selector receiving the output of the multiplier and the output of the 3-input selector and an adder/subtracter connected to the 2-input selector.

6. A clamping divider for clamping a result of a division to a maximum clamp value of 2^m (m being an integer) if a quotient of the division is equal to or larger than the maximum clamp value and to a minimum clamp value of 2ⁿ (n being an integer) if the quotient is equal to or smaller than the minimum clamp value, comprising:

(a) a priority encoder for receiving a divisor for standardizing the divisor to a value;

(b) an input barrel shifter for receiving the output of the priority encoder, the divisor and a dividend, shifting the divisor and the dividend;

(c) a bit shifter for shifting a divisor or a dividend of the division in a higher or lower direction by m bits when determining whether or not the quotient is equal to or greater than the maximum clamp value of "1" or below, in a higher or lower direction by n bits when determining whether or not the quotient is equal to or smaller than the minimum clamp value;

(d) a multiple accumulator (MAC) for subtracting the dividend or divisor shifted by the bit shifter from the divisor or dividend shifted by the input barrel shifter, and, according to a result of the subtraction, before calculating the quotient, determining whether or not the result of the division must be clamped to the maximum or minimum clamp value; and

(e) an output circuit for providing the result of the division according to the determination made by the MAC, wherein the output circuit comprises;

a 3-input selector for receiving the output of the MAC and the maximum and minimum clamp values; and

an output register for holding the output of the selector.

9. The clamping divider of claim 6, further comprising:

a ROM for receiving the output of the input barrel shifter through a register, wherein;

the output of the ROM is supplied to the MAC through a register and a selector.

10. The clamping divider of claim 9, further comprising an input selector connected to the input side of the input barrel shifter, to select one of the divisor and dividend.

11. A processor comprising:

(a) a clamping divider having;

a bit shifter for shifting a divisor or a dividend of a division in a higher or lower direction by m bits when determining whether or not a quotient of the division is equal to or greater, than a maximum clamp value, and in a higher or lower direction by n bits when determining whether or not the quotient is equal to or smaller than a minimum clamp value;

a multiple accumulator (MAC) for subtracting the dividend or divisor shifted by the bit shifter from the divisor or dividend, and according to a result of the subtraction and before calculating the quotient, determining whether or not a result of the division must be clamped to the maximum or minimum clamp value; and

an output circuit for providing the result of the division according to the determination made by the MAC;

(b) a unit for instructing the clamping divider to stop executing the division by a division instruction if the clamping divider determines that the result of the division execution must be clamped; and

(c) another unit for instructing the clamping divider to start a next division execution if a next division instruction follows just after the division instruction.

12. The processor of claim 11, wherein the maximum clamp value is set to "1" or below, the dividend is shifted like the divisor, the dividend is standardized like the divisor, and the MAC multiplies the shifted dividend by a reciprocal of the divisor, to find out the quotient.

13. A pipeline processing method with a sequence of cycles for clamping a result of a division to a maximum clamp value of 2^m (m being an integer) if a quotient of the division is equal to or larger than the maximum clamp value and to a minimum clamp value of 2ⁿ (n being an integer) if the quotient is equal to or smaller than the minimum clamp value, the sequence comprising the steps of:

shifting a divisor or a dividend of the division in a higher or lower direction by m bits by a bit shifter, subtracting the shifted dividend or divisor from the dividend or the divisor to determine whether or not the result of the division must be clamped to the maximum value, in one cycle;

shifting the divisor or dividend in a higher or lower direction by n bits by the bit shifter, subtracting the shifted dividend or divisor from the dividend or the divisor to determine whether or not the quotient is equal to or smaller than the minimum clamp value in another one cycle; and

calculating the quotient in a cycle, after the one and the another cycles.

14. The pipeline processing method of claim 13, wherein the maximum clamp value is set to "1" or below.

19. The pipeline processing method of claim 14, wherein the one cycle further include the steps of:

standardizing the divisor; and

shifting the divisor and the dividend by a barrel shifter.

15. A clamping divider for clamping a result of a division to a maximum clamp value of 2^m (m being an integer) if a quotient of the division is equal to or larger than the maximum clamp value and to a minimum clamp value of 2ⁿ (n being an integer) if the quotient is equal to or smaller than the minimum clamp value, comprising:

(a) a bit shifter for shifting a divisor or a dividend of the division in a higher or lower direction by m bits, and in a higher or lower direction by n bits;

(b) a multiple accumulator (MAC) for subtracting the dividend or divisor shifted by the bit shifter from the divisor or dividend, and according to a result of the subtraction and before calculating the quotient, determining whether or not the result of the division must be clamped to the maximum or minimum clamp value;

(c) a 3-input selector for receiving the divisor, a value of "2" and a rounding value, being connected to the MAC; and

(d) an output circuit for providing the result of the division according to the determination made by the MAC.

16. The clamping divider of claim 15, further comprising a priority encoder for receiving a divisor and standardizing the divisor to a value and an input barrel shifter for receiving the output of the priority encoder, the divisor and a dividend,

wherein the maximum clamp value is set to "1" or below, the dividend and the divisor are shifted by the input barrel shifter, and the MAC multiplies the shifted dividend by a reciprocal of the divisor to determine the quotient.

18. The clamping divider of claim 15, wherein the MAC has a multiplier, a 2-input selector receiving the output of the multiplier and the output of the 3-input selector and an adder/subtracter connected to the 2-input selector.

20. A pipeline processing method for clamping a result of a division to a maximum value of 2^m (m being an integer) and to a minimum clamp value of 2ⁿ (n being an integer), comprising the steps of:

storing a divisor and a dividend into registers, respectively, in a first cycle;

standardizing the divisor, shifting the divisor, shifting the dividend in a higher or lower direction by m bits, and subtracting the dividend from the divisor to determine whether or not the quotient is equal to or greater than the maximum clamp value, in a second cycle;

shifting the dividend in a higher or lower direction by n bits, and subtracting the dividend from the divisor to determine whether or not the quotient is equal to or smaller than the minimum clamp value, in a third cycle;

calculating an intermediate result in a fourth cycle;

calculating the quotient in a fifth cycle by using the intermediate result; and

outputting the quotient in a sixth cycle.

21. A pipeline processing method for clamping a result of a division to a maximum value of 2^m (m being an integer) and to a minimum clamp value of 2ⁿ (n being an integer), comprising the steps of:

storing a divisor and a dividend into registers, respectively, in a first cycle;

standardizing the divisor, shifting the divisor, shifting the dividend in a higher or lower direction by n bits, and subtracting the dividend from the divisor to determine whether or not the quotient is equal to or smaller than the minimum clamp value, in a second cycle;

shifting the dividend in a higher or lower direction by m bits, and subtracting the dividend from the divisor to determine whether or not the quotient is equal to or greater than the maximum clamp value, in a third cycle;

calculating an intermediate result, in a fourth cycle;

calculating the quotient in a fifth cycle by using the intermediate result; and

outputting the quotient, in a sixth cycle.

22. A pipeline processing method for clamping a result of a division to a maximum value of "1" or below and to a minimum clamp value of 2ⁿ (n being an integer), comprising the steps of:

storing a divisor and a dividend into registers, respectively, in a first cycle;

standardizing the divisor, shifting the divisor and dividend, and subtracting the dividend from the divisor to determine whether or not the quotient is equal to or greater than "1," in a second cycle;

shifting the dividend in a higher direction by n bits, and subtracting the dividend from the divisor to determine whether or not the quotient is equal to or smaller than the minimum clamp value, in a third cycle;

calculating an intermediate result, in a fourth cycle;

calculating the quotient, in a fifth cycle, by using the intermediate result; and

outputting the quotient in a sixth cycle.

23. A pipeline processing method for clamping a result of a division to a maximum value of "1" or below and to a minimum clamp value of 2ⁿ (n being an integer), comprising the cycles of:

storing a divisor and a dividend into registers, respectively, in a first cycle;

standardizing the divisor, shifting the divisor and dividend, shifting the dividend in a higher direction by n bits, and subtracting the dividend from the divisor to determine whether or not the quotient is equal to or smaller than the minimum clamp value, in a second cycle;

subtracting the dividend from the divisor to determine whether or not the quotient is equal to or greater than "1," in a third cycle;

calculating an intermediate result, in a fourth cycle;

calculating the quotient, in a fifth cycle, using the intermediate result; and

outputting the quotient, in a sixth cycle.