ASIC

Double Precision Floating Point Mathematic Unit IP Core

General Description:

The FPMU-DP is a Double precision Floating Point Coprocessor designed to assist CPU in performing the floating point mathematic computations. The FPMU-DP directly replaces C software functions by equivalent and very fast hardware operations which significantly accelerate system performance. The core does not require any programming, so there is no need for any modifications being made in the main software. Everything is done automatically during software compilation by the FPMU-DP C driver.

The FPMU-DP is designed to operate with the DP8051 / DP80390 microcontrollers as well as any other 8-, 16- and 32-bit processor. Drivers for all popular 8051 C compilers are delivered together with the FPMU-DP package. The FPMU-DP also supports popular 32-Bit NIOS II and MicroBlaze processors. The C drivers for these processors are delivered with the FPMU-DP for free.

The FPMU-DP uses the specialized CORDIC and standard algorithms to compute math functions. It supports addition, subtraction, multiplication, division, square root, comparison, and trigonometric functions: sine, cosine, tangent and arctangent. It has built-in conversion instructions from integer type to floating point type and vice versa. The input numbers format is according to IEEE-754 standard.

The FPMU-DP supports double and single precision real numbers, 8-bit, 16-bit and 32-bit integers. The FPMU-DP is prepared to use with 8-, 16- and 32-bit processors.

The FPMU-DP is a technology independent design that can be implemented in a variety of process technologies.

Key Features:

► Direct replacement for C double, float software functions such as: +, -, *, /,==, !=,>=, <=, <, >
► Configurability of all available functions
► C interface supplied for all popular compilers: GNU C/C++, 8051 compilers
► C interface supplied for NIOS II and MICROBLAZE processors
► No programming required
► IEEE-754 Double precision real format support – double type
► IEEE-754 Single precision real format support – float type
► 8-bit, 16-bit 32-bit and 52-bit integers format supported – integer types
► Flexible arguments and result registers location
► Performs the following functions:
   o FADD, FSUB – addition, subtraction
   o FMUL, FDIV – multiplication, division
   o FSQRT – square root
   o FXAM – examine input data
   o FUCOM – comparison
   o FSIN, FCOS – sine, cosine
   o FTAN – tangent
   o FATAN – arctangent
   o FCLD, FILD – 8-bit, 16-bit integer to double
   o FLLD, FELD – 32-bit, 52-bit integer to double
   o FCST, FIST – double to 8-bit, 16-bi integer
   o FLST, FEST – double to 32-bit, 52-bit integer
   o FFLD – float to double
   o FFST – double to float
► Exceptions built-in routines
► Masks each exception indicator:
   o Precision lack PE
   o Underflow result UE
   o Overflow result OE
   o Invalid operand IE
   o Division by zero ZE
   o Denormal operand DE
► Fully configurable
► Fully synthesizable
► Static synchronous design
► Positive edge clocking and no internal tri-states
o Scan test ready

The table and figures below illustrates the system with FPMU-DP performance improvements for typical 32-bit RISCCPU.
The FPMU-DP floating point instructions performance has been compared to standard C library functions delivered with every commercial C compiler. Each program was executed in the same system environments. Number of clock periods were measured between input data loading into work registers and output result storing after operation. The results are placed in tables below.
Improvement has been computed as a number of clock cycles required by the CPU to compute FP operation, by the number of clocks required to compute the same operation by system of CPU with FPMU-DP:

32-Bit RISC Based System:

The table below shows performance improvements of the sample 32-bit-RISC CPU with FPMU-DP, compared to the same system without the FPMU-DP coprocessor.

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Function	CPU CLK	DFPMU_DP CLK	Improvement
Arithmetic operations	-	-
-
Addition	1376	114	12.0
Subtraction	1338	114	11.7
Multiplication	1628	153	10.6
Division	2964	197	15.0
Square Root	3030	141	21.5
Total	-	-	14.1
Trigonometric operations	-	-	-
Sine	18730	360	52.0
Cosine	21798	360	60.8
Tangent	37500	383	97.9
Arcs Tangent	36790	467	78.7
Total	-	-	72.4
Average speed improvement:	-	-	55.0

Units

Interface

Makes interface between external device and core internal 32-bit modules. It contains data, control and status registers. It can be configured to work with 8-, 16- and 32-bit processors..

¹^{- data bus can be configured as 8-, 16-
or 32- bit depends on processor’s bus size}
²^{- address bus is aligned to work with 8- (3:0),
16- (3:1) or 32- (4:2) bit processors}

Control Unit

It manages execution of all instructions and internal operation required to execute particular function.

Align

It performs the numbers analyze against IEEE-754 standard compliance. Information about the data classes are passed as result to appro-priate internal module.

Exponent

It performs operations on exponent part of number. The addition, subtraction, shifting, comparison and conversion operations are executed in this module. It contains exponents and work registers.

Mantissa

It performs operations on mantissa part of number. The addition, subtraction, multiplication, division, square root, comparison and conversion operations are executed in this module. It contains mantissas and work registers.

Shifter

It performs mantissa shifting during normalization, denormalization operations. Information about shifted-out bits are stored for rounding process.

CORDIC

CORDIC performs trigonometric operations on input data. The sine, cosine, tangent and arctangent operations are executed in this module. It contains three work registers.

Performance:

FPMU-DP implementation results for ALTERA devices. The all features have been included.

Implementation	Speed grade	Logic Cells	Frequency [MHz]
CYCLONE	-6	7070	77
CYCLONE-II	-6	7080	68
STRATIX	-5	7070	82
STRATIX II	-3	5290	109

FPMU-DP implementation results for XILINX devices. The all features have been included.

Implementation	Speed grade	Slices	Frequency [MHz]
VIRTEX-II	-6	3820	77
VIRTEX-II pro	-7	3810	99
VIRTEX-4	-11	3700	93
VIRTEX-5	-1	2150	121

Price:

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