9BIT mode - read the address value

Stefano De Blasiis

I have a TM4C123AH tiva processor.

I have configured the UART in 9-Bit Mode with interrupt

UARTConfigSetExpClk(UART1_BASE, SysCtlClockGet(), 38400,
                        (UART_CONFIG_WLEN_8 | UART_CONFIG_STOP_ONE |
                         UART_CONFIG_PAR_ZERO));
    UARTFIFODisable (UART1_BASE);
    UARTIntEnable(UART1_BASE, UART_INT_RX | UART_INT_9BIT | UART_INT_FE);
UART_INT_FE | UART_INT_PE));
    UART9BitAddrSet(UART1_BASE, 0x83, 0xFF);        // slave address 03 fisso
    UART9BitEnable(UART1_BASE);
    IntEnable(INT_UART1);

When the interrupt routine is execute I cannot read the Address value

  ulStatus = UARTIntStatus(UART1_BASE, true);
  UARTIntClear(UART1_BASE, ulStatus);

  if (ulStatus & UART_MIS_9BITMIS)
    {
    while(UARTCharsAvail(UART1_BASE))
      {
      // NEVER ENTER HERE
      bufferRx[cntbufferRx] = UARTCharGet(UART1_BASE);
      cntbufferRx ++;
      }
    cntbufferRx = 0;
    }
   else  if (ulStatus & UART_MIS_RXMIS)
    {
    while(UARTCharsAvail(UART1_BASE))
      {
      bufferRx[cntbufferRx] = UARTCharGet(UART1_BASE);
      cntbufferRx ++;
      }
    }
}

Is it normal not read the data address in 9-BIT mode ?

Thanks

over 11 years ago

0 Amit Ashara over 11 years ago

TI__Guru**** 244400 points

Hello Stefano,

If I read the post, then the Address on Match is never put in the data register. Only the subsequent data bytes are made available.

Regards

Amit

0 Stefano De Blasiis over 11 years ago in reply to Amit Ashara

Intellectual 530 points

But . . . if, I use the addres mask like this :

UART9BitAddrSet(UART1_BASE, 0x83, 0x80);

How can I understan which address has been recognized if I can't read it ?

very strange

0 Amit Ashara over 11 years ago in reply to Stefano De Blasiis

TI__Guru**** 244400 points

Hello Stefano,

TIVA UART in 9-bit mode does not support Address extraction. This is applicable when using Mask bits as well.

Regards

Amit

0 Petrei over 11 years ago in reply to Amit Ashara

Guru 26105 points

Hi,

Please note the order of operations is always important - in your code:

UARTFIFODisable (UART1_BASE);

UARTIntEnable(UART1_BASE, UART_INT_RX | UART_INT_9BIT | UART_INT_FE);

is not operating well, since the UARTIntEnable() silently enables also the FIFO, so best is to use UARTFIFODisable after UARTIntEnable().

Second, your code setting the address:

UART9BitAddrSet(UART1_BASE, 0x83, 0xFF); // slave address 03 fisso

seems to be wrong - 0x83 is not the address of slave 0x03 - just use 0x03 - the ninth bit setting the address is outside a byte. Seems you are writing software for a slave - keep in mind that after getting an address you must change the operating mode to receive data - I attached two files also from TI, written for Stellaris, showing how to manage sticky bit - read, understand, combine with actual Tiva to get it working.

When testing be sure you have a good 9-bit sender.

1777.nb_uart.zip

Petrei