XMC 1000 32-bit Microcontroller Series for Industrial Applications Math Coprocessor (MA TH) AP32307 Application Note About this document Scope and purpose This document describes how to use the MATH Coprocessor for the XMC 32-bit Microcontroller. The document includes code snippets and examples for a variety of use cases. Intended audience This document is intended for engineers who are developing applications that require math-intensive computations with the XMC Microcontroller series. Applicable Products XMC130x XMC140x DAVE ™ References Infineon: Example code: http://www.infineon.com/XMC1000 Tab: Documents Infineon: XMC Lib, http://www.infineon.com/DAVE Infineon: DAVE™, http://www.infineon.com/DAVE Infineon: XMC Reference Manual, http://www.infineon.com/XMC1000 Tab: Documents Infineon: XMC Data Sheet, http://www.infineon.com/XMC1000 Tab: Documents V1.0 1 2015-07 Math Coprocessor (MATH) AP32307 Table of Contents Table of Contents About this document .....................................................................................................................1 Table of Contents ..........................................................................................................................2 1 1.1 1.2 MATH Coprocessor Overview .........................................................................................3 Features ............................................................................................................................................... 3 MATH Library ....................................................................................................................................... 3 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Division Operation ........................................................................................................4 Configuration for Signed or Unsigned division operation ................................................................. 4 Configuration for starting the division operation .............................................................................. 4 Poll for the result to be ready ............................................................................................................. 5 Generate an Interrupt when result is ready ....................................................................................... 5 Divide by Zero Error ............................................................................................................................ 5 Using XMC Lib for DIV operations ....................................................................................................... 6 DIVS Benchmarking Results ................................................................................................................ 7 3 3.1 3.2 3.3 3.4 3.5 3.5.1 3.6 3.6.1 3.6.2 3.6.3 3.7 CORDIC ........................................................................................................................9 Configuration for CORDIC operation .................................................................................................. 9 Configuration for starting CORDIC operation .................................................................................. 10 Poll for the result to be ready ........................................................................................................... 11 Generate an Interrupt on completion .............................................................................................. 11 Using XMC Lib for CORDIC calculation.............................................................................................. 11 Calculating exp(z)........................................................................................................................ 13 CORDIC Examples .............................................................................................................................. 13 Calculating Vector Magnitude and Angle ................................................................................... 13 Calculating ln(x) .......................................................................................................................... 14 Calculating sqrt(x) ....................................................................................................................... 15 CORDIC Benchmarking Results ........................................................................................................ 16 4 4.1 4.2 4.3 4.4 4.5 Result Chaining........................................................................................................... 17 Data Compatibility between 32-bit DIV and 24-bit CORDIC............................................................. 17 Transfer of data from DIV to CORDIC ................................................................................................ 18 Transfer of data from CORDIC to DIV ................................................................................................ 18 Handling Busy Flags during Result Chaining ................................................................................... 18 Result Chaining Example .................................................................................................................. 18 5 Appendix .................................................................................................................... 20 6 Revision History .......................................................................................................... 21 Application Note 2 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 MATH Coprocessor Overview 1 MATH Coprocessor Overview The Math Coprocessor (MATH) module provides assistance for math-intensive computations. The module comprises of two independent sub-blocks which are executed in parallel to the CPU core. The two subblocks are: A 32-bit Divider Unit (DIV) for signed and unsigned division functions A 24-bit CORDIC (COrdinate Rotation DIgital Computer) for trigonometric, linear and hyperbolic functions 1.1 Features The MATH module includes the following features: Divide function with operand pre-processing and result post-processing CORDIC Coprocessor for computation of trigonometric, hyperbolic and linear functions Support kernel clock to interface clock ratio 2:1 for faster execution Support result chaining between the Divider Unit and CORDIC Coprocessor 1.2 MATH Library The MATH library is a collection of Application Programming Interfaces (APIs) to compute common mathematical operations such as division, modulus and trigonometric functions. The APIs configure the respective registers of the MATH sub-blocks to perform the requested calculations. The library is provided as part of the XMC Library (XMC Lib) from Infineon. The APIs provided in the MATH library can be categorized as Blocking and Non-blocking. The blocking APIs poll for the result by reading the result register. This adds wait states to the bus until the result is ready. While waiting for the result, all other operations are blocked, hence the name. The non-blocking APIs start the desired calculations and then control is returned to the calling thread. This allows other operations to continue. The user can check if a calculation has ended by polling the busy flag of the MATH Coprocessor. When the busy flag is cleared, the user can read the calculation result by calling the GetResult APIs. Note: The occurence of interrupts during the execution of non-blocking APIs may lead to erroneous results. For example, the execution of a divide instruction ( ‘/’ ) in an interrupt service routine during the execution of a non-blocking API may give erroneous results. Application Note 3 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 Division Operation 2 Division Operation DIVS supports the truncated division operation, which is the ISO C99 standard and the most popular choice among modern processors: q = D divide by d r = D modulus by d “D” is the dividend (DVD register) “d” is the divisor (DVS register) “q” is the quotient (QUOT register) “r” is the remainder (RMD register) 2.1 Configuration for Signed or Unsigned division operation Configuration is via the DIVCON.USIGN bit: DIVCON.USIGN = 0 Signed division DIVCON.USIGN = 1 Unsigned division 2.2 Configuration for starting the division operation There are two methods for starting the division operation. Either: 1. Set the ST bit 2. Or have the division operation start automatically by loading a value into the DVS register Starting the division operation by setting the ST bit MATH->DIVCON = (1<<MATH_CON_ST_MODE_Pos); // DIVCON.STMODE = 1 // Calculation start when ST bit is set MATH->DVD = 0x12345678; // Load the dividend value MATH->DVS = 0x11223344; // Load the divisor value MATH->DIVCON |= (1<<MATH_CON_ST_Pos); // DIVCON.ST = 1 // ST bit is set. The division begins Starting the division operation automatically MATH->DIVCON = (0<<MATH_CON_ST_MODE_Pos); // DIVCON.STMODE = 0 // Calculation start when write to DVS register MATH->DVD = 0x12345678; // Load the dividend value MATH->DVS = 0x11223344; // Load the divisor value, the division begin Application Note 4 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 Division Operation 2.3 Poll for the result to be ready The division operation takes 35 kernel clock cycles. The BSY flag is set to 1 when the division operation starts. On completion, the quotient and remainder values are available in the QUOT and RMD registers, and the BSY flag is cleared. DIVST.BSY = 0 DIV is not running any division operation DIVST.BSY = 1 DIV is still running a division operation // Insert code for division operation to start while(MATH->DIVST); // Wait until DIV is ready (Not busy) // Insert code to read out result 2.4 Generate an Interrupt when result is ready When the division is finished, the Divider event flag EVFR.DIVEOC is set. This can trigger an interrupt request to the NVIC by enabling the EVIER.DIVEOCIEN bit. This event flag can only be cleared by a software write to the EVFCR.DIVEOCC bit: MATH->EVIER = (1<<MATH_EVIER_DIVEOCIEN_Pos); // EVIER.DIVEOCIEN = 1 // End of divider calculation interrupt generation is enabled NVIC_EnableIRQ(7); // Enabled MATH interrupt node // Insert code for division operation to start …………………………………………………………………………………………… // Inside the MATH ISR MATH->EVFCR = (1<<MATH_EVFCR_DIVEOCC_Pos); // EVFCR.DIVEOCC = 1 // Clear Divider end of calculation flag in EVFR 2.5 Divide by Zero Error If a division operation is started with the divisor value equal to 0, the EVFR.DIVERR flag is set. The interrupt request to the NVIC can be generated by enabling it with EVIER.DIVERRIEN. This event flag can only be cleared by a software write to the EVFCR.DIVERRC bit. MATH->EVIER = (1<<MATH_EVIER_DIVERRIEN_Pos); // EVIER.DIVERRIEN = 1 // Divider error interrupt generation is enabled NVIC_EnableIRQ(7); // Enabled MATH interrupt node // Insert code for division operation to start …………………………………………………………………………………………… // Inside the DIV_ERROR ISR MATH->EVFCR = (1<<MATH_EVFCR_DIVERRC_Pos); // EVFCR.DIVERRC = 1 // Clear the Divider error event flag in EVFR Application Note 5 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 Division Operation 2.6 Using XMC Lib for DIV operations The MATH Library provides alternate implementations of the ARM Embedded Application Binary Interface (AEABI) functions for division and modulus operations. These alternate implementations use the DIV subblock to perform the operations. The following examples demonstrate their usage: Blocking division operation uint32_t a = 5000; uint32_t b = 250; uint32_t c = a / b; Blocking modulus operation uint32_t a = 5000; uint32_t b = 240; uint32_t c = a % b; In both examples above, the ‘/’ and ‘%’ operators are automatically recognized and the respective AEABI functions are called to perform the operations using the DIV sub-block. Note: Only signed and unsigned integer division and modulus operations are supported by the MATH Library. Non-blocking division operation /* variable initialization */ uint32_t calculation_dividend = 5000; uint32_t calculation_divisor = 250; uint32_t calculation_result; /* unsigned division calculation */ XMC_MATH_DIV_UnsignedDivNB(calculation_dividend,calculation_divisor); while(XMC_MATH_DIV_IsBusy()); // wait for calculation to end calculation_result = XMC_MATH_DIV_GetUnsignedDivResult(); In the example above, the XMC_MATH_DIV_IsBusy() API is used to check for the end of calculation. Alternatively, the user can also perform other operations and read the CORDIC calculation result only after a determined number of clock cycles or use an interrupt. The following example demonstrates the usage of an interrupt. Application Note 6 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 Division Operation Non-blocking modulus operation /* variable initialization */ uint32_t calculation_dividend = 5000; uint32_t calculation_divisor = 240; uint32_t calculation_result; /* configure DIV end-of-calculation interrupt */ XMC_MATH_EnableEvent(XMC_MATH_EVENT_DIV_END_OF_CALC); NVIC_SetPriority(MATH0_0_IRQn,3); NVIC_EnableIRQ(MATH0_0_IRQn); /* unsigned modulus calculation */ XMC_MATH_DIV_UnsignedModNB(calculation_dividend,calculation_divisor); /* MATH Interrupt Handler */ void MATH0_0_IRQHandler(void) { uint32_t calculation_result; XMC_MATH_ClearEvent(XMC_MATH_EVENT_DIV_END_OF_CALC); calculation_result = XMC_MATH_DIV_GetUnsignedModResult(); } 2.7 DIVS Benchmarking Results The performance of the Divider is evaluated by benchmarking the execution time of a division operation running on the MATH Library against that of a similar operation running on a standard C library. The execution time is measured in terms of the number of MCLK cycles. The conditions for the benchmarking are as follows: Execution time refers to complete function execution, inclusive of co-processor configuration, writing of operands and state checking. The ratio of PCLK to MCLK is 2:1. Compilers from Infineon, Keil™ and IAR were used. Application Note 7 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 Division Operation Table 1 Benchmarking results for division operation Compiler Number of MCLK cycles With MATH Library With Standard C Library IAR EWARM v7.10 99 712 Keil™ Vision v5.10 95 230 114 415 TM DAVE v3.1.10 From the benchmarking results, a division operation with the MATH library can be up to 7 times faster than a similar operation with the standard C library. Application Note 8 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 CORDIC 3 CORDIC The CORDIC algorithm is a useful convergence method for 24-bit computation of trigonometric (circular), linear (multiply-add), hyperbolic and related functions. It allows performance of vector rotation not only in the Euclidian plane, but also in the Linear and Hyperbolic planes. CORDX, CORDY, and CORDZ are Data registers which are used to initialize the X, Y and Z parameters. Figure 1 CORDIC data register structure CORRX, CORRY, and CORRZ are Result registers from the CORDIC calculation. Figure 2 CORDIC result register structure 3.1 Configuration for CORDIC operation Table 2 gives an overview of the different CORDIC operating modes. X, Y and Z represent the initial data and Xfinal, Yfinal & Zfinal represent the final result data when the CORDIC computation is completed. Table 2 Operating Modes of CORDIC Function Circular Linear Application Note Rotation Mode Xfinal = K[X cos(Z) - Y sin(Z)] / MPS Vectoring Mode Yfinal = K[Y cos(Z) + X sin(Z)] / MPS Yfinal = 0 Zfinal = 0 Zfinal = Z + atan(Y / X) K ≈ 1.646760258121 K ≈ 1.646760258121 Xfinal = X / MPS Xfinal = X / MPS Yfinal = [Y + X Z] / MPS Yfinal = 0 Zfinal = 0 Zfinal = Z + Y / X 9 Xfinal = K sqrt(X2+Y2) / MPS V1.0, 2015-07 Math Coprocessor (MATH) AP32307 CORDIC Function Hyperbolic Rotation Mode Xfinal = k[X cosh(Z) + Y sinh(Z)] / MPS Vectoring Mode Yfinal = k[Y cosh(Z) + X sinh(Z)] / MPS Yfinal = 0 Zfinal = 0 Zfinal = Z + atanh(Y / X) k ≈ 0.828159360960 k ≈ 0.828159360960 Xfinal = k sqrt(X2-Y2) / MPS The different modes are configured via the ROTVEC and MODE fields in the CON control register. CON.ROTVEC = 0 Vectoring Mode CON.ROTVEC = 1 Rotation Mode CON.MODE = 00b Linear Mode CON.MODE = 01b Circular Mode CON.MODE = 11b Hyperbolic Mode The X and Y Magnitude Prescaler (MPS) prevents the result data from overflowing. At the end of calculation, the computed values of X and Y are each divided by the MPS factor to yield the final result. Note: Refer to the appendix for other mathematical calculations supported by CORDIC. 3.2 Configuration for starting CORDIC operation There are two methods to start the CORDIC operation: Set the ST bit Or have the operation automatically start by loading a value into the CORDX register Starting the CORDIC operation by setting the ST bit MATH->CON = (1<<MATH_CON_ST_MODE_Pos); // CON.STMODE = 1; // Calculation start when ST bit is set to 1 MATH->CORDZ = 0x12345600; MATH->CORDY = 0x11223300; MATH->CORDX = 0x33221100; MATH->CON |= (1<<MATH_CON_ST_Pos); // CON.ST = 1; // Start the CORDIC operation Starting the CORDIC operation automatically MATH->CON = (0<<MATH_CON_ST_MODE_Pos); // CON.STMODE = 0; // Calculation start with a write to CORDX MATH->CORDZ = 0x12345600; MATH->CORDY = 0x11223300; MATH->CORDX = 0x33221100; // Load CORDX value and start CORDIC operation Application Note 10 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 CORDIC 3.3 Poll for the result to be ready The CORDIC operation takes 62 kernel clock cycles. The BSY flag is set when operation starts. On completion, the BSY flag is cleared. STATC.BSY = 0 CORDIC is not computing any calculation STATC.BSY = 1 CORDIC is still computing a calculation // Insert code for CORDIC to start while((MATH->STATC)&(1<<MATH_STATC_BSY_Pos)); // wait until CORDIC is ready (Not busy) // Insert code to read out result 3.4 Generate an Interrupt on completion At the end of the CORDIC computation, the event flag EVFR.CDEOC is set. An interrupt request to the NVIC can be triggered by enabling the EVIER.CDEOCIEN bit. This event flag can only be cleared by a software write to the EVFCR.CDEOCC bit. MATH->EVIER = (1<<MATH_EVIER_CDEOCIEN_Pos); // EVIER.CDEOCIEN = 1 // End of CORDIC calculation interrupt generation is enabled NVIC_EnableIRQ(7); // Enable MATH interrupt node // Insert code for CORDIC to start ……………………………………………………………………………………….. // Inside the MATH ISR MATH->EVFCR = (1<<MATH_EVFCR_CDEOCC_Pos); // EVFCR.CDEOCC = 1 // Clear CORDIC end of calculation event flag in EVFR 3.5 Using XMC Lib for CORDIC calculation The MATH Library supports the following CORDIC calculations: Trigonometric: Sin, Cos, Tan, Atan Hyperbolic: Sinh, Cosh, Tanh When using the XMC Lib APIs for calculations where the input data is an angle, it is essential that the input angle is converted using the following equation: Input_angle = (angle_in_rad) * 8388608 / π For example, to calculate cos(π/6), the input angle is: Input_angle = (π/6) * 8388608 / π = 1398101 or 0x155555 Application Note 11 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 CORDIC Example using Blocking APIs /* variable initialization */ XMC_MATH_Q0_23_t angle = 0x2AAAAA; // (pi/3)*8388608/pi XMC_MATH_Q0_23_t calculation_result; /* cosine of angle calculation */ calculation_result = XMC_MATH_CORDIC_Cos(angle); Example using Non-Blocking APIs /* variable initialization */ XMC_MATH_Q0_23_t angle = 0x155555; // (pi/6)*8388608/pi XMC_MATH_Q0_23_t calculation_result; /* cosine of angle calculation */ XMC_MATH_CORDIC_CosNB(angle); while(XMC_MATH_CORDIC_IsBusy()); // wait for calculation to end calculation_result = XMC_MATH_CORDIC_GetCosResult(); In the non-blocking API example above, the XMC_MATH_CORDIC_IsBusy() API is used to check for the end of the calculation. The user can instead perform other operations and read the CORDIC calculation result only after a determined number of clock cycles or use an interrupt. The following example demonstrates the use of an interrupt. Example using Non-Blocking API and Interrupt /* variable initialization */ XMC_MATH_Q0_23_t angle = 0x860A91; // (pi/3)*8388608/pi /* configure CORDIC end-of-calculation interrupt */ XMC_MATH_EnableEvent(XMC_MATH_EVENT_CORDIC_END_OF_CALC); NVIC_SetPriority(MATH0_0_IRQn,3); NVIC_EnableIRQ(MATH0_0_IRQn); /* cosine of angle calculation */ XMC_MATH_CORDIC_CosNB(angle); /* MATH Interrupt Handler */ void MATH0_0_IRQHandler(void) { Application Note 12 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 CORDIC XMC_MATH_Q0_23_t calculation_result; XMC_MATH_ClearEvent(XMC_MATH_EVENT_CORDIC_END_OF_CALC); calculation_result = XMC_MATH_CORDIC_GetCosResult(); } 3.5.1 Calculating exp(z) It is known that: exp(z) = sinh(z) + cosh(z) The following example demonstrates how exp(0.5) can be calculated using the XMC Lib. /* variable initialization */ XMC_MATH_Q0_23_t angle = 0x145F30; // 0.5*8388608/pi XMC_MATH_Q0_23_t calculation_result; /* hyperbolic sine of angle calculation */ calculation_result = XMC_MATH_CORDIC_Sinh(angle); /* hyperbolic cosine of angle calculation (also final result) */ calculation_result += XMC_MATH_CORDIC_Cosh(angle); Although the MATH Library supports only the abovementioned calculations, the CORDIC sub-block is capable of computing many other calculations. These calculations can be performed by manually configuring the registers of CORDIC. Refer to Figure 6 for a more complete view on the different computations that can be performed with CORDIC. 3.6 CORDIC Examples This section provides some CORDIC use-cases. 3.6.1 Calculating Vector Magnitude and Angle The following example illustrates the use of CORDIC in the Circular Vectoring Mode for the calculation of the magnitude and angle of two vectors. Table 3 CORDIC Circular Vectoring Mode Function Circular Vectoring Mode 2 2 Xfinal = K sqrt(X +Y ) / MPS Yfinal = 0 Zfinal = Z + atan(Y / X) K ≈ 1.646760258121 Application Note 13 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 CORDIC MATH->CON = 0x0002; // MODE = 01b, Circular Mode // ROTVEC = 0, Vectoring Mode // ST_MODE = 0, Auto start when CORDX is written MATH->CORDZ = 0; // Load the initial angle value MATH->CORDY = (vector2<<8); // Load the magnitude of vector 2 MATH->CORDX = (vector1<<8); // Load the magnitude of vector 1 // CORDIC will automatically start while((MATH->STATC)&(1<<MATH_STATC_BSY_Pos)); // wait until CORDIC is ready (Not busy) Result_Mag = MATH->CORRX; // Read out the result Result_Ang = MATH->CORRZ; 3.6.2 Calculating ln(x) It is known that: ln(x) = 2*atanh[(x-1)/(x+1)] CORDIC can be used in the Hyperbolic Vectoring mode for the calculation above by setting the initial input data as follows: X=x+1 Y=x-1 The following example illustrates the calculation of ln(variable_x) using CORDIC. MATH->CON = 0x0006; // MODE = 11b, Hyperbolic Mode // ROTVEC = 0, Vectoring Mode // ST_MODE = 0, Auto start when CORDX is written MATH->CORDZ = 0; // Load the initial angle value MATH->CORDY = ((variable_x-1)<<8); // Load (x-1) MATH->CORDX = ((variable_x+1)<<8); // Load (x+1) // CORDIC will automatically start while((MATH->STATC)&(1<<MATH_STATC_BSY_Pos)); // wait until CORDIC is ready (Not busy) Result = (MATH->CORRZ>>8); Application Note // Read out the result of atanh 14 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 CORDIC Result = 2*Result; // final result is scaled by 8388608/pi Note: The result of this calculation has a scaling of 8388608/π. 3.6.3 Calculating sqrt(x) It is known that: sqrt(x) = sqrt[(x+0.25)2-(x-0.25)2] CORDIC can be used in the Hyperbolic Vectoring mode for the calculation above by setting the initial input data as follows: X = (x + 0.25) / k Y = (x - 0.25) / k where k = 0.82815936960 The user should ensure that the input data lie within the domain of convergence, meaning atanh|Y/X| ≤ 1.11 radians. The following example demonstrates the square root calculation of a Q1.8 number. The calculated result is a Q5.12 number. #define GAIN 0x0135 // (2^8)/0.82815936960 uint32_t number = 0x01C0; MATH->CON = 0x0006; // MODE = 11b, Hyperbolic Mode // ROTVEC = 0, Vectoring Mode // ST_MODE = 0, Auto start when CORDX is written MATH->CORDZ = 0; // Load the initial angle value MATH->CORDY = ((GAIN*(number-0x40))<<8); // Load (x-0.25)/k MATH->CORDX = ((GAIN*(number+0x40))<<8); // Load (x+0.25)/k // CORDIC will automatically start while((MATH->STATC)&(1<<MATH_STATC_BSY_Pos)); // wait until CORDIC is ready (Not busy) Result = (MATH->CORRX>>8); Application Note // Read out the result 15 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 CORDIC 3.7 CORDIC Benchmarking Results The performance of the CORDIC co-processor is evaluated by benchmarking the execution time of a cosine calculation running on the MATH Library against that of a similar operation running on a standard C library. The execution time is measured in terms of the number of MCLK cycles. The conditions for the benchmarking are as follows: Execution time refers to complete function execution, inclusive of co-processor configuration, writing of operands and state checking. The ratio of PCLK to MCLK is 2:1. Compilers from Infineon, Keil™ and IAR were used. Table 4 Benchmarking results for cosine calculation Compiler Number of MCLK cycles With MATH Library With Standard C Library IAR EWARM v7.10 234 4574 Keil Vision v5.10 238 6514 258 9832 TM DAVE v3.1.10 From the benchmarking results, a cosine calculation with the MATH library can be up to 38 times faster than a similar operation with the standard C library. Application Note 16 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 Result Chaining 4 Result Chaining The MATH Coprocessor supports result chaining between the DIV and CORDIC modules. The DIV result can be passed to the input of the CORDIC data register. Similarly, the CORDIC result can also be passed to the input of the DIV DVD and DVS registers. GLBCON.DVDRC and GLBCON.DVSRC 000b No result chaining 001b QUOT register is the input to DIV 010b RMD register is the input to DIV 011b CORRX register is the input to DIV 100b CORRY register is the input to DIV 101b CORRZ register is the input to DIV GLBCON.CORDXRC, GLBCON.CORDYRC and GLBCON.CORDZRC 00b No result chaining 01b QUOT register is the input to DIV 10b RMD register is the input to DIV 4.1 Data Compatibility between 32-bit DIV and 24-bit CORDIC The data and result register for the DIV are assigned to bits[0 to 31]. Figure 3 DIV data and result register structure The data and result register for the CORDIC are assigned to bits[8 to 31]. Figure 4 CORDIC data and result register structure Application Note 17 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 Result Chaining 4.2 Transfer of data from DIV to CORDIC The DIV’s quotient final value can be left-shifted by 8 to fit into the CORDIC data register format. DIVCON.QSCNT Number of bits the quotient is shifted after the division DIV.QSDIR = 0 Left shift DIV.QSDIR = 1 Right shift 4.3 Transfer of data from CORDIC to DIV The DIV’s final divisor value can be right-shifted by 8 when it is updated by the CORDIC result register. DIVCON.DVSSRC Number of bits the divisor is shifted right before the division DIV.QSDIR = 0 Left-shift 4.4 Handling Busy Flags during Result Chaining When the DIV result is chained to the CORDIC’s CORDX, if CON.ST_MODE = 0 the start of the DIV calculation sets the DIV’s busy flag and also sets the CORDIC’s busy flag. After completion of the DIV operation, the result is written into the DIV’s register and CORDX. The DIV’s busy flag is not immediately cleared. Instead, both the DIV and CORDIC busy flags are cleared after the CORDIC calculation is completed. Figure 5 Busy flags during Result Chaining The rule described above is applied in the other direction when the CORDIC result is chained to DIV’s DVS register and DIVCON.STMODE = 0. 4.5 Result Chaining Example The following example illustrates the use of result chaining by updating the input data of DIV’s divisor using the CORDIC’s CORRX output result. Application Note 18 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 Result Chaining /* DVSRC = 011b, DVS result will be updated when CORRX has new result */ MATH->GLBCON = XMC_MATH_DIV_DVSRC_CORRX_IS_SOURCE; /* STMODE = 0, Auto start when DVS is written */ /* DVSSRC = 8, DVS value right shifted by 8 */ MATH->DIVCON = (0<<MATH_DIVCON_STMODE_Pos)+(8<<MATH_DIVCON_DVSSRC_Pos); /* Preload the dividend value first */ MATH->DVD = 0x12345678; /* MODE = 01b, Circular Mode */ /* ROTVEC = 0, Vectoring Mode */ /* ST_MODE = 0, Auto start when CORDX is written */ MATH->CON = XMC_MATH_CORDIC_OPERATING_MODE_CIRCULAR + XMC_MATH_CORDIC_ROTVEC_MODE_VECTORING + (0<<MATH_CON_ST_MODE_Pos); /* Load the initial angle value */ MATH->CORDZ = 0; /* Load the magnitude of Vector2 */ MATH->CORDY = (0x123456<<8); /* Load the magnitude of Vector1 */ MATH->CORDX = (0x112233<<8); // CORDIC will automatically start // ………………………………………………………………………………….. // CORDIC result to DVS will start DIV while(XMC_MATH_DIV_IsBusy()); // wait until DIV is ready (Not busy) Result = MATH->QUOT; Application Note // Read out the result 19 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 Appendix 5 Appendix Figure 6 CORDIC Coprocessor Operating Modes and Corresponding Result Data Application Note 20 V1.0, 2015-07 Math Coprocessor (MATH) AP32307 Revision History 6 Revision History Current Version is V1.0, 2015-07 Page or Reference Description of change V1.0, 2015-07 Initial Version Application Note 21 V1.0, 2015-07 Trademarks of Infineon Technologies AG AURIX™, C166™, CanPAK™, CIPOS™, CIPURSE™, CoolGaN™, CoolMOS™, CoolSET™, CoolSiC™, CORECONTROL™, CROSSAVE™, DAVE™, DI-POL™, DrBLADE™, EasyPIM™, EconoBRIDGE™, EconoDUAL™, EconoPACK™, EconoPIM™, EiceDRIVER™, eupec™, FCOS™, HITFET™, HybridPACK™, ISOFACE™, IsoPACK™, iWafer™, MIPAQ™, ModSTACK™, my-d™, NovalithIC™, OmniTune™, OPTIGA™, OptiMOS™, ORIGA™, POWERCODE™, PRIMARION™, PrimePACK™, PrimeSTACK™, PROFET™, PRO-SIL™, RASIC™, REAL3™, ReverSave™, SatRIC™, SIEGET™, SIPMOS™, SmartLEWIS™, SOLID FLASH™, SPOC™, TEMPFET™, thinQ!™, TRENCHSTOP™, TriCore™. Other Trademarks Advance Design System™ (ADS) of Agilent Technologies, AMBA™, ARM™, MULTI-ICE™, KEIL™, PRIMECELL™, REALVIEW™, THUMB™, µVision™ of ARM Limited, UK. ANSI™ of American National Standards Institute. AUTOSAR™ of AUTOSAR development partnership. Bluetooth™ of Bluetooth SIG Inc. CATiq™ of DECT Forum. COLOSSUS™, FirstGPS™ of Trimble Navigation Ltd. EMV™ of EMVCo, LLC (Visa Holdings Inc.). EPCOS™ of Epcos AG. FLEXGO™ of Microsoft Corporation. HYPERTERMINAL™ of Hilgraeve Incorporated. MCS™ of Intel Corp. IEC™ of Commission Electrotechnique Internationale. IrDA™ of Infrared Data Association Corporation. ISO™ of INTERNATIONAL ORGANIZATION FOR STANDARDIZATION. MATLAB™ of MathWorks, Inc. MAXIM™ of Maxim Integrated Products, Inc. MICROTEC™, NUCLEUS™ of Mentor Graphics Corporation. MIPI™ of MIPI Alliance, Inc. MIPS™ of MIPS Technologies, Inc., USA. muRata™ of MURATA MANUFACTURING CO., MICROWAVE OFFICE™ (MWO) of Applied Wave Research Inc., OmniVision™ of OmniVision Technologies, Inc. Openwave™ of Openwave Systems Inc. RED HAT™ of Red Hat, Inc. RFMD™ of RF Micro Devices, Inc. SIRIUS™ of Sirius Satellite Radio Inc. SOLARIS™ of Sun Microsystems, Inc. SPANSION™ of Spansion LLC Ltd. Symbian™ of Symbian Software Limited. TAIYO YUDEN™ of Taiyo Yuden Co. TEAKLITE™ of CEVA, Inc. TEKTRONIX™ of Tektronix Inc. TOKO™ of TOKO KABUSHIKI KAISHA TA. UNIX™ of X/Open Company Limited. VERILOG™, PALLADIUM™ of Cadence Design Systems, Inc. VLYNQ™ of Texas Instruments Incorporated. VXWORKS™, WIND RIVER™ of WIND RIVER SYSTEMS, INC. ZETEX™ of Diodes Zetex Limited. Last Trademarks Update 2014-07-17 www.infineon.com Edition 2015-07 Published by Infineon Technologies AG 81726 Munich, Germany © 2015 Infineon Technologies AG. All Rights Reserved. Do you have a question about any aspect of this document? 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