Error using UART1 as a FIQ

I have a firmware runing fine with UART1 as a normal IRQ.

Recently I realize that I should use UART1 as a FIQ to be sure that the communication works fine.

As an IRQ I had the this defintions:
"...
VICVectAddr7=(unsigned long) ISR_UART1;
VICVectPriority7=0x00000008;
VICIntSelect &= 0xFFFFFF7F;
VICIntEnable |= 0x00000080;
..."
"...
void ISR_UART1 (void) __attribute__ ((interrupt("IRQ")));
...."

void ISR_UART1
{ .... .... cTmp=U1IIR; VICVectAddr = 0x00000000;
}

As a FIQ I changed to:

As an IRQ I had the this defintions:
"...
VICIntSelect |= 0x00000080;
VICIntEnable |= 0x00000080;
..."
"...
void FIQ_Handler(void) (void) __attribute__ ((interrupt("FIQ")));
...."

void FIQ_Handler(void)
{ DEBUG = 1
DEBUG = 0
DEBUG = 1 ISR_UART1(); //it is the only one FIQ so I call imediatly this funciton
DEBUG = 0
}

With the osciloscope I can see the the Debug going '1'->'0'->'1' but it never leaves the function and don't get the final '0'.

Can anyone help me with this???