Why does'nt it work!!!!!(dual uart)

[tkvenki]

Hi all,

I'm using a ST16C2550 (Dual UART) to interface to my controller.
I'm using POLLING MODE in controlling the UART.
I'm writing the following configuration to the UART:

Uart_Write(LCR, 0x80); //Divisor latch enable

Uart_Write(DLL, 0x0C); //set the baud rate to 9600
Uart_Write(DLH, 0x00);

Uart_Write(LCR, 0x03); //8data bits-1 stop bit-no parity
Uart_Write(FCR, 0x01); //Enable rx and tx FIFO
Uart_Write(IER, 0x00); //Disable all interrupts.

In my code:

while (1)
{
OSTimeDlyMillisec(1000);
if(Uart_Read(LSR) & 0x01)
{
ch = Uart_Read(RXTX);
printf("\n BYTE IN RX BUFFER = %x\n",ch);
Uart_Write(RXTX, ch);
}
}

I'm polling the LSR register. THe LSB of LSR gets high as soon as a byte is present in the FIFO. Then if the check is successful i read the data and send back the same.

BUt when i read the LSR(in my read routine), I'm getting only the default value(0x60). The value is not getting updated at all. I used my oscilloscope and confirmed that the data is coming till the UART pins.

Please help me out in identifying the problem.

Best Regards
tkvenki

 

[vlawp]

"BUt when i read the LSR(in my read routine), I'm getting only the default value(0x60). The value is not getting updated at all"

tkvenki,

*In the polling mode, LSR[0] will be a logic 1 as long as there is 1 byte in the FIFO. It will be 0 otherwise.
*In the interrupt mode the receive data ready bit(LSR[0]) is set as soon as a character is transferred from the shift register to the FIFO. It is reset when the FIFO is empty.

So, by the time you read the LSR[0], it probably must have reset because you sent and received only one byte. Try sending and receiving multiple bytes and read the LSR[0] when atleast one byte is present in the FIFO.