XC167 ASC Interrupt, ASCx_RIC

I am attempting to use an interrupt to service data received from ASC1. I cannot find information on setting the ASCx_RIC register in the Infineon manuals. I have found some examples that use values of 0x0071 or 0x0044 but these may not be correct for my application.

Currently I am able to trip an interrupt when I transmit data, but the serial data is not being passed to the isr. The isr works when called from a loop using getchar, but I would like to use an interrupt. I am using this method on a PIC processor, but have been unable to make it work using the XC167.

// Code to setup ASC1
void serial_init_1(int RValue)  // Radio Header
{
  P3  |= 0x0001;                // SET PORT 3.0 OUTPUT LATCH (TXD)
  DP3 |= 0x0001;                // SET PORT 3.0 DIRECTION CONTROL (TXD OUTPUT)
  DP3 &= 0xFFFD;            // RESET PORT 3.1 DIRECTION CONTROL (RXD INPUT)
  ASC1_TIC = 0x80;              // SET TRANSMIT INTERRUPT FLAG
  ASC1_RIC = 0x0044;            // Enable serial receive interrupt level 1
  ASC1_BG  = RValue;            // SET BAUDRATE
  ASC1_CON = 0x8011;            // SET SERIAL MODE
  ALTSEL0P3 |= 0x0003;          // Configure port pins for serial interface 1
  RSTCON    &=  0x40;       // Configure ResetOut
}


// Code for interrupt
void ASC1_RxIsr(void) interrupt 0x49 // ASC1 Receive
{
        ASC1_RIC = 0x00;
        radio_isr(0);
        ASC1_RIC = 0x44;
}


// Radio ISR
int radio_isr(char mode)
{
        c = (char) getchar_1();
        ... ... ....
}