UART5YRXXFIFOH长度常数的目的是什么？

以上代码来自MCC生成的文件。该文件是UPART库的一部分，用于PIC24F设备。UART5YRXXFIFOH长度常数的目的是什么？我想，如果选择了“3/4”或“接收缓冲区已满”的中断而不是“数据可用”中断，则应该将其更改为3或4。这个假设我是对的还是这个常数被用于其他事物？提前THNX



      以下为原文

   
#define UART5_TX_FIFO_LENGTH 1
#define UART5_RX_FIFO_LENGTH 1

void __attribute__ ( ( interrupt, no_auto_psv ) ) _U5RXInterrupt( void )
{
    int count = 0;

    while((count < UART5_RX_FIFO_LENGTH) && (U5STAbits.URXDA == 1))
    {
        count++;

        *uart5_obj.rxTail = U5RXREG;

        uart5_obj.rxTail++;

        if(uart5_obj.rxTail == (uart5_rxByteQ + UART5_CONFIG_RX_BYTEQ_LENGTH))
        {
            uart5_obj.rxTail = uart5_rxByteQ;
        }

        uart5_obj.rxStatus.s.empty = false;
        
        if(uart5_obj.rxTail == uart5_obj.rxHead)
        {
            //Sets the flag RX full
            uart5_obj.rxStatus.s.full = true;
            break;
        }
        
    }

    IFS6bits.U5RXIF = false;
   
}


Hi
The above code is from an MCC generated file. The file is a part of the UART library for a pic24f device
What is the purpose of the UART5_RX_FIFO_LENGTH constant? I was thinking that this should be changed to 3 or 4 in  case the interrupt on "3/4" or "receive buffer full" was selected instead of the "data available" interrupt. Am I right with this assumption or is this constant used for something else?
Thnx in advance