Reason for tampering of bitband mapping address at run time - arm

Question

I am using bit banding to set and clear a GPIO6[1] of LPC1857 using Keil.
The mapping address in bit band region to set GPIO6[1] comes 0x43EC4304
The mapping address in bit band region to clear GPIO6[1] comes 0x43EC5384
THE GPIO gets set successfully but does not get cleared.
When checked on debugger, it is observed that mapping address to clear the GPIO6[1] was getting set to 0x43EC5000. Thus the GPIO does not get clear.
Can someone please help understand why this is happening ?
And how can I resolve this mapping address setting to wrong address at run time ?
Following is code snippet:
/*In "main.c"*/
int main()
{
... //System initialization
... //GPIO init
...
Toggle_Peri();
}
/*In "Peri.c"*/
/* Bit band PERIPHERAL definitions */
#define BITBAND_PERI_REF 0x40000000 //Start Address of PeripheRALS
#define BITBAND_PERI_BASE 0x42000000 //Start Address of Peripheral Bit Band Alias Region
/* Basic bit band function definition */
#define BITBAND_PERI(a,b) ((BITBAND_PERI_BASE + ((a-BITBAND_PERI_REF)*(0x20)) + (b*(0x04)))) // Convert GPIO address
#define BITBAND_PERI_SetClearBit(a,b) ((*(volatile uint32_t *) (BITBAND_PERI(a,b))) = 1)
/*Note: Base Address of GPIO = 0x400F 4000*/
#define PERI_GPIO_ADDRESS_S 0x400F6218 //For GPIO6[1] set
#define PERI_GPIO_ADDRESS_C 0x400F629C //For GPIO6[1] clear
#define PERI_GPIO_BIT 1
...
...
...
...
void Toggle_Peri(void)
{
BITBAND_PERI_SetClearBit(PERI_GPIO_ADDRESS_S,PERI_GPIO_BIT); //Set the pin
Delay(0xFFFF);
BITBAND_PERI_SetClearBit(PERI_GPIO_ADDRESS_C,PERI_GPIO_BIT); //Clear the pin
Delay(0xFFFF);
}