ARM CM4 FPU execption

Hi Anuj,

there would be several cases to produce the floating point execeptions.
I would show the below examples.

FPExc_InvalidOp
     +infinity + (–infinity)
FPExc_DivideByZero
     normalized number / zero
FPExc_Overflow
     maximum normalized number + 1
FPExc_Underflow
     minumum normalized number - 1
FPExc_Inexact
     maximum normalized number + minumum normalized number
FPExc_InputDenorm
     operand is denormalized number

In Cortex-M4 case, the enable bits seem not to be implemented.
So, you can only see the accumulated exception results in FPSCR.

Best regards,

Yasuhiko Koumoto.

Hi Anuj,

there would be several cases to produce the floating point execeptions.
I would show the below examples.

FPExc_InvalidOp
     +infinity + (–infinity)
FPExc_DivideByZero
     normalized number / zero
FPExc_Overflow
     maximum normalized number + 1
FPExc_Underflow
     minumum normalized number - 1
FPExc_Inexact
     maximum normalized number + minumum normalized number
FPExc_InputDenorm
     operand is denormalized number

In Cortex-M4 case, the enable bits seem not to be implemented.
So, you can only see the accumulated exception results in FPSCR.

Best regards,

Yasuhiko Koumoto.

Hello Yasuhiko,

Thanks for your email. To be precise I am using Cortex M4F.

Regards,

Anuj

Hello,

I'm very sorry but I had given wrong information.
The overflow and underflow conditions were wrong.
I have corrected them in the actual code.
I have verified them on my FRDM-K64F board.

The CPU of the board is Cortex-M4F.

#include <stdio.h>
#include <stdlib.h>
#include "fsl_device_registers.h"
#include "fsl_uart_driver.h"
#include "fsl_clock_manager.h"
#include "board.h"
#ifdef DEBUG
#include "fsl_debug_console.h"
#endif
/*******************************************************************************
 * Definitions
 ******************************************************************************/
#define USE_STDIO_FUNCTIONS  /* Define this symbol to use STDIO functions */

/*******************************************************************************
 * Global Variables
 ******************************************************************************/
/*******************************************************************************
 * Prototypes
 ******************************************************************************/
void FPSCR_CLR(void);
int  FPSCR_GET(void);
/*******************************************************************************
 * Code
 ******************************************************************************/
/********************************************************************/
int main (void)
{
  
  union {
    float f;
    int  i;
  } X, Y, Z;
  
    /***************************************************************************
    *  RX buffers
    **************************************************************************/
    /*! @param receiveBuff Buffer used to hold received data */
    uint8_t receiveBuff[19] = {0};
    /* Initialize standard SDK demo application pins */
    hardware_init();
    /* Configure the UART TX/RX pins */
    configure_uart_pins(BOARD_DEBUG_UART_INSTANCE);
    /* Call this function to initialize the console UART.  This function
      enables the use of STDIO functions (printf, scanf, etc.) */
    dbg_uart_init();
    
    /*  Print the initial banner */
    printf("\r\nFPU ExceprionLinpack Bnechmark\n\n\r");
    
    //FPU_Enable();
      
    printf("FPExc_InvalidOp\n\r");
    /* +infinity + (?infinity) */
    FPSCR_CLR();
    X.i = 0x7f800000;
    Y.i = 0xff800000;
    Z.i = 0x00000000;
    Z.f = X.f + Y.f;
    printf("RES=%08x FPSCR=%08x\n\r", Z.i, FPSCR_GET());
  
    printf("FPExc_DivideByZero\n\r");
    /* normalized number / zero */
    FPSCR_CLR();
    X.i = 0x3f800000;
    Y.i = 0x00000000;
    Z.i = 0x00000000;
    Z.f = X.f / Y.f;
    printf("RES=%08x FPSCR=%08x\n\r", Z.i, FPSCR_GET());
  
    printf("FPExc_Overflow\n\r");
    /* maximum normalized number * maximum normalized number */
    FPSCR_CLR();
    X.i = 0x7f7fffff;
    Y.i = 0x7f7fffff;
    Z.i = 0x00000000;
    Z.f = X.f * Y.f;
    printf("RES=%08x FPSCR=%08x\n\r", Z.i, FPSCR_GET());
  
    printf("FPExc_Underflow\n\r");
    /* minumum normalized number /  maximum normalized number */
    FPSCR_CLR();
    X.i = 0x00800000;
    Y.i = 0x7f7fffff;
    Z.i = 0x00000000;
    Z.f = X.f / Y.f;
    printf("RES=%08x FPSCR=%08x\n\r", Z.i, FPSCR_GET());
  
    printf("FPExc_Inexact\n\r");
    /* maximum normalized number + minumum normalized number */
    FPSCR_CLR();
    X.i = 0x7f7fffff;
    Y.i = 0x00800000;
    Z.i = 0x00000000;
    Z.f = X.f + Y.f;
    printf("RES=%08x FPSCR=%08x\n\r", Z.i, FPSCR_GET());
  
    printf("FPExc_InputDenormt\n\r");
    /* operand is denormalized number */
    FPSCR_CLR();
    X.i = 0x00000001;
    Y.i = 0x00000000;
    Z.i = 0x00000000;
    Z.f = X.f + Y.f;
    printf("RES=%08x FPSCR=%08x\n\r", Z.i, FPSCR_GET());
  
    while(1)
    {
    }
}
void FPSCR_CLR(void)
{
  int tmp=(1<<24);
  asm volatile ("VMSR FPSCR,%0\n" : "=r" (tmp) : "0" (tmp));
}
int  FPSCR_GET(void)
{
  int tmp;
  asm volatile ("VMRS %0,FPSCR\n" : "=r" (tmp) : "0" (tmp));
  return tmp;
}

Best regards,
Yasuhiko Koumoto.