CN101630243A - Transcendental function device and method for realizing transcendental function utilizing same - Google Patents

Abstract

The invention discloses a transcendental function device and a method for realizing the transcendental function utilizing the same. The device comprises a preprocessing unit, a processing unit and a post-processing unit. The processing unit is composed of a counter register 1, a counter register 2, an X register and a processing passage thereof, a Y register and a processing passage thereof, a Z register and a processing passage thereof, and a control state machine. By utilizing an HPOR CORDIC device, one-one correspondence relation between indexes of a median generated in processing and a change of the counter is established, and the change of the counter register 2 represents the change of the indexes, therefore only a magnitude portion is processed to eliminate an index operation and mantissa match exponents in a floating decimal CORDIC. The device further overcomes shortcomings of large delay of the floating decimal CORDIC device and poor processing precision of a fixed point CORDIC device, and the realization price of hardware is much low.

Description

Transcendental function device and the method that realizes transcendental function with this device

Technical field

The present invention relates to a kind of transcendental function device.Also relate to the method that realizes transcendental function with this transcendental function device.

Background technology

Document 1 " patent No. is the United States Patent (USP) of US20060200510 " discloses a kind of CORDIC angle treating apparatus, have a unit for scaling in this device, before the CORDIC conversion, this device is done the conversion that moves to left to the data of input earlier, processing finishes, and adopts opposite conversion process again.This device can improve the processing accuracy of CORDIC angle by the round-off error in the shift left operation minimizing processing.But because fixed-point data represents that the error that causes is very big, the precision that this innovative approach obtains improves more limited in the CORDIC conversion.

Document 2 " patent No. is the United States Patent (USP) of US20060233284 " discloses a kind of CORDIC whirligig, and this device adopts fixed point CORDIC conversion to realize the angle rotation, in the iterative process of CORDIC, has adopted carry at random.This device is in order to improve the precision of processing, with traditional round off nearby to be improved at random round off.But the error that rounds off at random under extreme case is very big, influences the instability of system.

Document 3 " patent No. is the United States Patent (USP) of US20030097388 " discloses a kind of vector rotation CORDIC device, this device adopt two single-precision numbers and, the index of this single-precision number is to be the signed number at the end with 2.By take and form, can reduce the error that angle is handled.But in the CORDIC device that with the floating number is process object, this structure can not reduce the delay that floating-point is handled.

With reference to Fig. 5 and Fig. 6, known transcendental function device comprises pretreatment unit, processing unit and post-processing unit.In floating-point CORDIC device, processing unit comprises exponential part and magnitude portion, owing to adopted the floating-point structure, the processing accuracy height, but each iteration need be carried out index to the normalization of rank, mantissa's addition, floating number and round off, and circuit delay is big, and realizes complicated.In fixed point CORDIC device, processing unit is made up of the integer structure, handles required hardware costs and delay is all very little, and still the round-off error that causes is bigger.Therefore, in the transcendental function device, floating-point CORDIC device and fixed point CORDIC device all exist defective to overcome.

Summary of the invention

Postpone big, the low deficiency of fixed point CORDIC structure treatment precision in order to overcome floating-point CORDIC structural circuit, the invention provides a kind of transcendental function device, adopt the HPOR CORDIC hardware configuration of high precision, order iteration to generate transcendental function, the index variation of the intermediate variable that will produce during this hardware configuration will be handled is mapped on the iterations, eliminate the index operation of floating-point transcendental function device, can not introduce unnecessary round-off error simultaneously.This HPOR CORDIC transcendental function device possesses the low characteristics that postpone, hang down hardware costs, high processing accuracy simultaneously.

The present invention also provides the method for utilizing this transcendental function hardware unit to realize transcendental function.At first input value is carried out pre-service, input value is transformed into certain limit.The exponential quantity of input value after the generation pre-service, exponential quantity, the mantissa value of input value are input to HPOR CORDIC unit as input quantity, HPOR CORDIC starts working through after the initialization, result is standardized at last again, and is converted to floating number output.

The technical solution adopted for the present invention to solve the technical problems: a kind of transcendental function device, comprise pretreatment unit, processing unit and post-processing unit, be characterized in: described processing unit is by counter register 1, counter register 2, X register and processing path thereof, y register and processing path thereof, Z register and processing path thereof, control state machine is formed, to the X register, y register and Z register input initial value, control state machine is sent processing command, the X register is handled path, y register handles path and Z register processing path was handled its corresponding register value respectively in each clock period, result is saved in the corresponding register once more, every processing once, counter register 1 adds 1, counter register 2 adds 1, when the value of counter register 1 and counter register 2 equals preset value, control state machine is sent and is ceased and desisted order, X register and y register output result.

A kind of method of utilizing above-mentioned transcendental function device to realize transcendental function is characterized in may further comprise the steps:

(a) input value pre-service when realizing trigonometric function, is converted to input value [π/4, π/4], when realizing hyperbolic function, input value is converted to [1/2,1/2];

(b) handle the index of pretreated input value, and expand three in mantissa's most significant digit and lowest order respectively;

(c) with the exponential quantity of input value as the counter initial value, the mantissa of input value is as Z register initial value, according to instruction to the X register, the y register initialize;

(d) processing unit work;

In the processing, only magnitude portion is handled, exponential part does not participate in handling;

(e) according to the exponential part of Counter Value generation result, according to the X register, the value of y register generates magnitude portion, and result is done normalization, returns step (a).

The invention has the beneficial effects as follows: owing to adopt HPOR CORDIC device, one-to-one relationship is set up in the index of the intermediate value of generation and the variation of counter in the processing, index variation has been represented in the variation of counter register 2, therefore in processing, only there is magnitude portion to participate in handling, eliminated that index among the floating-point CORDIC is handled and mantissa to rank, this device has overcome simultaneously that floating-point CORDIC device processing delay is big, the shortcoming of fixed point CORDIC device processing accuracy difference, and hardware realizes that cost is very little.

Below in conjunction with drawings and Examples the present invention is elaborated.

Description of drawings

Fig. 1 is the structured flowchart of transcendental function device of the present invention.

Fig. 2 is the detail drawing of pretreatment unit among Fig. 1.

Fig. 3 is the detail drawing of processing unit among Fig. 1.

Fig. 4 is the detail drawing of post-processing unit among Fig. 1.

Fig. 5 is the structured flowchart of known floating-point transcendental function device.

Fig. 6 is the structured flowchart of known fixed point transcendental function device.

Embodiment

With reference to Fig. 1～4, the present invention is at the textural transcendental function device that adopts HPOR CORDIC structure.Whole device is made up of pretreatment unit, processing unit and post-processing unit three parts.Pretreatment unit is used for the input value of transcendental function is carried out conversion, and processing unit is responsible for implementing concrete processing, and post-processing unit is done the normalization processing to the output result of processing unit.Processing instruction that the pretreatment unit receiving processor sends and floating-point source operand, the selector switch of pretreatment unit and divider can be done normalization to source operand according to the difference of processor instruction and handle: if processor instruction is hyperbolic function, source operand is normalized to [1/2,1/2] in, if processor instruction is a trigonometric function, source operand is normalized to [π/4, π/4].Source operand after pretreatment unit will be standardized is decomposed into sign bit S, exponent bits and mantissa position, handle the index E of normalization back source operand, and the mantissa of this source operand is expanded to 70bit by 64 count Man, S, E after pretreatment unit will be handled, Man output to processing unit.Processing unit makes up S and Man and be saved in the Z register, and E is saved in the counter 2, according to instruction counter register 1, X register, y register is done initialization simultaneously.After initialization was finished, under the control of state machine, processing unit was started working, and iteration is 64 times altogether, and required parameter is kept among the ROM in the processing, by state machine control access.The back output result of finishing dealing with X, Y and ES.Post-processing unit generates intermediate result according to ES, X, Y, middle result is standardized and rounds off handle and output.

The information flow direction of entire circuit is: processor sends transcendental function instruction and source operand, instruction of pretreatment module receiving processor and source operand, source operand is normalized to the data field of setting according to processor instruction, and source operand is decomposed into S, Man and E, this three number is kept in Z register, the counter register 2 as the input of processing unit.Processing unit is exported result X, Y and ES after initialization, 64 iteration, post-processing unit receives this three numbers and sign bit, and it is combined into floating number, does normalization at last, rounds off and operate and output.

The transcendental function device realizes that the method for transcendental function is specific as follows:

(1) source operand of the instruction of the transcendental function of pretreatment unit receiving processor and 80 IEEE754 floating-point formats.

(2) pretreatment unit is done the normalization processing according to processor instruction to source operand:, source operand is converted to [π/4, π/4] if processor instruction is a trigonometric function, if processor instruction is hyperbolic function, source operand is converted to [1/2,1/2].

(3) pretreatment unit is done decomposition to normalized source operand according to sign bit S, exponent bits, mantissa position, the index E of source operand after the processing pre-service, and expand three in the Man of mantissa most significant digit and lowest order respectively.

(4) processing unit initialization: processing unit receives S, E, Man, respectively S and Man is kept in Z register and the counter register 2, and putting counter register 1 is 0, and the output initial value is to the X register from ROM, and putting y register is 0.

(5) processing unit is started working, and has only mantissa participate in to handle in the processing, and exponent bits does not participate in handling, each clock period iteration once, 64 clock period of iteration altogether.

(6) post-processing unit receives the processing unit processes result: X, Y and ES, and according to sign bit S composition floating number.

(7) post-processing unit is done the normalization and the processing of rounding off to the result of floating-point format.

(8) the output result turns back to step (1).

Can find out that from carrying out on the flow process this device has following characteristics: at first, in pretreatment unit, the floating-point source is operated Number decomposes, and source operand is decomposed into sign bit, exponent bits and mantissa position, and sign bit and exponent bits do not participate in processing procedure, Only as the initial value of counter, in the iterative process of processing unit, the displacement of X register, y register and Z register is grasped The mantissa that do, add operation only has floating number participates in processing, and has eliminated the index of floating-point CORDIC device to rank and mantissa's specification Change operation, reduced circuit delay, the processing accuracy of not losing circuit simultaneously.

Claims (2)

1, a kind of transcendental function device, comprise pretreatment unit, processing unit and post-processing unit, it is characterized in that: described processing unit is by counter register 1, counter register 2, X register and processing path thereof, y register and processing path thereof, Z register and processing path thereof, control state machine is formed, to the X register, y register and Z register input initial value, control state machine is sent processing command, the X register is handled path, y register handles path and Z register processing path was handled its corresponding register value respectively in each clock period, result is saved in the corresponding register once more, every processing once, counter register 1 adds 1, counter register 2 adds 1, when the value of counter register 1 and counter register 2 equals preset value, control state machine is sent and is ceased and desisted order, X register and y register output result.

2, a kind of method of utilizing the described transcendental function device of claim 1 to realize transcendental function is characterized in may further comprise the steps:

(a) input value pre-service when realizing trigonometric function, is converted to input value [π/4, π/4], when realizing hyperbolic function, input value is converted to [1/2,1/2];

(b) handle the index of pretreated input value, and expand three in mantissa's most significant digit and lowest order respectively;

(c) with the exponential quantity of input value as the counter initial value, the mantissa of input value is as Z register initial value, according to instruction to the X register, the y register initialize;

(d) processing unit work;

In the processing, only magnitude portion is handled, exponential part does not participate in handling;

(e) according to the exponential part of Counter Value generation result, according to the X register, the value of y register generates magnitude portion, and result is done normalization, returns step (a).

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