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LPC2378 UART0 Rx FIFO Trigger Level problem

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Karthik Venkatesh
Joined: 2015-11-27
Posts: 15


I am trying to understand the UART0 Receive Trigger level feature available in LPC2378.

Problem Description:

I set FCR register for the Trigger level of 4 bytes.

And reading the IIR register for identifying whether Threshold level interrupt has occured.

If yes, then am reading the RXRBR receive buffer 4 times.

When I run this on LPC2378, for the very 1st byte input, interrupt is triggered.

Find the captured output attached herewith.

What am I doing wrong.

Note: I referred an old thread in this forum reg. the same issue, but in vein.

Code is as following:

#include "UART.h"
#include "PLL_CONFIG.h"
#include "PRINT.h"

char a[4];

void UART0_INIT(int baud_rate)
        unsigned int k;

        k = SET(baud_rate);

        PCONP |= 1<<3; //power to UART0
        PCLKSEL0 |= 0x40; //pclk = cclk
        PINSEL0 |=  0x00000050;

        U0IER |= (1<<1) | (1<<0);          //Enabling the TX and RX interrupts

        U0LCR = 0x83;

        U0DLM = (k/256);
        U0DLL = (k%256);

        U0LCR = 0x03;

        U0FCR |= (1<<6) | (1<<0);         //Setting the RX Trigger level to 4


void send_data(char a)

         U0THR = a;

void get_data()

        while(U0IIR & 0x04) {                             //Checking if 'Trigger level reached' interrupt flag is set
              a[0]=U0RBR;                                    //Reading 1st RX Byte from U0RBR
              a[1]=U0RBR;                                    //Reading 2nd RX Byte from U0RBR
              a[2]=U0RBR;                                    //Reading 3rd RX Byte from U0RBR
              a[3]=U0RBR;                                    //Reading 4th RX Byte from U0RBR
              for(char i=0;i<4;i++) {
			printf("\n\rChars u entered are %c",a[i]);


int main(void)




void delay(int delay)
int g,k;

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