Everything stops during flash/EE erase

I am using an ADuC7021 for my embedded application. one task is to drive a 7-seg display, another task is to store parameters in Flash/EE. The refresh display function is called every 2.5ms. The flash erase is called when the next flash page is not blank.

The problem I have is that when the flash page is erased, everything else stops for 24ms. This causes a beat in the display. I have been looking at running the relevant sections of code from RAM during Flash erase, but this does not appear to have any effect - it still all stops.

I have generated a small test program, the object of which is to demonstrate something (anything) running during flash erase. I am simply toggling a pin and monitoring it on a scope, I then erase a Flash page and can see a 24ms gap in the toggling.

The test code is:

// test program running at absolute minimum overhead to investigate running code
// through a Flash erase cycle

#define MUX0       0x00200000   // output:   0 0 1 0 0 0 0 0 = 0x20
#define MUX1       0x00400000   // output:   0 1 0 0 0 0 0 0 = 0x40
#define MUX2       0x00800000   // output:   1 0 0 0 0 0 0 0 = 0x80

#define FEE_ERASE_WRITE_DIS     0x0000   // 0b00000000 00000000 Default
#define FEE_ERASE_WRITE_EN      0x0008   // 0b00000000 00001000

#include <ADuC7021.h>

void setbit( int signal)
{
   GP0SET = signal;   // set output bit
   GP0SET = 0;
}

void clrbit( int signal)
{
   GP0CLR = signal;   // Clear output bit
   GP0CLR = 0;
}

int main(void)
{
   int x;
   x = 0;

   GP0CON = 0x00001003;                   // set port 0 GPIO pins
   GP0DAT = 0xF0E00000;                   // set outputs

   while (   10000 > x++)                  // limit run time
   {
       setbit(MUX0);                       // toggle output pin
       clrbit(MUX0);

      if (0 == x % 1000)                  // periodically erase flash/EE
      {
         FEEMOD = FEE_ERASE_WRITE_EN;      // enable erase write
         FEEADR = 0x7FFF;                  // write to address register
         FEECON = ERASE_PAGE;               // write to command register
         FEEMOD = FEE_ERASE_WRITE_DIS;      // disable erase write
      }

   }
}

using this scatter file:

LR_IROM1 0x00080000 0x0000F800  {    ; load region size_region
  ER_IROM1 0x00080000 0x0000F800  {  ; load address = execution address
   *.o (RESET, +First)
   *(InRoot$$Sections)
   .ANY (+RO)
  }
  RW_IRAM1 0x00010000 0x00002000  {  ; RW data
    minimalram.o (+RO +ZI +RW)
   .ANY (+RW +ZI)
  }
}

What am I missing?