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    ARM Uart Theory

    Uploaded by

    Amit
    The document discusses the UART configuration for an ARM7 microcontroller. It describes the two UART ports, UART0 and UART1, with UART0 used for both programming and serial communication using a 16-byte buffer. It provides register details for UART0 including the receive buffer, transmit holding register, interrupt enable register, and baud rate generation. The document gives an example UART0 initialization program and interrupt handler to receive serial data at 9600 baud and store it in a buffer.

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    ARM Uart Theory

    Uploaded by

    Amit
    27 views5 pages
    The document discusses the UART configuration for an ARM7 microcontroller. It describes the two UART ports, UART0 and UART1, with UART0 used for both programming and serial communication using a 16-byte buffer. It provides register details for UART0 including the receive buffer, transmit holding register, interrupt enable register, and baud rate generation. The document gives an example UART0 initialization program and interrupt handler to receive serial data at 9600 baud and store it in a buffer.

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    The document discusses the UART configuration for an ARM7 microcontroller. It describes the two UART ports, UART0 and UART1, with UART0 used for both programming and serial communication using a 16-byte buffer. It provides register details for UART0 including the receive buffer, transmit holding register, interrupt enable register, and baud rate generation. The document gives an example UART0 initialization program and interrupt handler to receive serial data at 9600 baud and store it in a buffer.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    27 views5 pages

    ARM Uart Theory

    Uploaded by

    Amit
    The document discusses the UART configuration for an ARM7 microcontroller. It describes the two UART ports, UART0 and UART1, with UART0 used for both programming and serial communication using a 16-byte buffer. It provides register details for UART0 including the receive buffer, transmit holding register, interrupt enable register, and baud rate generation. The document gives an example UART0 initialization program and interrupt handler to receive serial data at 9600 baud and store it in a buffer.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 5

    UART:

     ARM7 has 2 UARTS UART0 and UART1


     UART 0 is used as serial communication as well as
    for on board Programming of ARM7
     UART 1 is used as serial communication only.
     16 byte buffer for UART0 and UART1
     Built in baud rate generator

    U0RBR: Receive buffer register:(Serial buffer 8 bit)

    The data received from uart0 pin is stored in this buffer.


    The U0RBR is the top byte of the RX FIFO register
    contains the oldest character received and can be read
    (Receive) via bus interface,
    U0THR: Transmit holding register:( 8 bit)
    The top byte is the newest character in TX FIFO and can
    be written (Transmit) via bus interface.
    U0IER: Interrupt Enable register: 8 bit
    Bit0:Rx data Enable
    U0TER: Transmit Enable register: 8 bit
    Bit7: Transmit Enable
    Baud Rate generation formula:

    So in order to get to get a baud rate of 9600 the values are


    as follows:
    Pclk 12 Mhz, Required Baud rate = 9600
    9600 = 12000000/16(16*U0DLM+U0DLL)
    16(16*U0DLM+U0DLL) = 12000000/9600
    U0DLM+U0DLL = 78 / 256 = 4.9 =5
    Assume U0DLM =0
    So U0 DLL =5
    U0LCR: Line Control Register

    In the program , U0LCR = 03Hex


    0:1 word length selection
    So here we are selecting
    8 bit data length , 1 stop bit ,Parity disabled
    U0LSR:
    U0LSR: LineLine Status
    Status register
    Register
    U0LSR0 is set to 1 when U0RBR holds an unread
    character and is cleared RX FIFO is empty.
    UART program:
    uint UART0Init( uint baudrate )
    {
    uint Fdiv;
    PINSEL0 |= 0x00000005;// Enable RxD1 and TxD1, RxD0 and TxD0
    00000000000000000000000000000101
    Fdiv =( Fpclk / 16*16 ) / baudrate ;//(12000000/9600)/256= 5
    U0DLM = Fdiv / 256; // 5
    U0DLL = Fdiv % 256; // 0
    U0LCR = 0x03; //8 bit character length
    U0FCR = 0x07; // Clear and Enable TX and RX FIFO

    U0IER = IER_RBR | IER_THRE | IER_RLS; // Enable UART0 interrupt


    // RBR= Receive data available interrupt
    //THRE= Transmit hold Register
    //RLS= Receive line status
    }
    void UART0Handler (void) __irq //Serial Interrupt handler

    if ( IIRValue == IIR_RLS ) /* Receive Line status */


    //There are errors or break in interrupt
    return

    else if ( IIRValue == IIR_RDA ) /* Receive Data Available */


    {
    //New data available in U0RBR

    DataBuffer[Uart0Count] = U0RBR; //Read the Character from


    U0RBR into µC RAM (DataBuffer[Uart0Count])

    Uart0Count++; //Increment µC RAM location


    Rxcnt = RXCNT ; //Reload timer 200
    RxFlag = 1 ; // Valid data has started
    // RxFlag=1 && Rxcnt==0
    }
    Timer is running at 1 msec and if our baud rate is 9600 bits per
    second then it comes to 1 msec per byte.
    So, when we receive a byte from serial port we reload the timer for
    200 msec time out.
    If next data is received before time out (200 msec) then the timer is
    again reset to time out.
    If there is no data interrupt until time out (200 msec) then it is
    assumed that the serial data is over and we can come out of Serial
    interrupt service routine. (Rxcnt==0)
    Serial Device
    PC/RF/IR/FP etc.

    RS232 Logic (+9v –9v) Baud rate =9600 ,8 bit

    RS 232 driver IC

    TTL Logic (0v - +5v ) Baud rate =9600 ,8 bit


    µC
    UART0 /1

    Here the µC receives the data at the specified Baud rate 9600.
    µC receives the data from URBR register (serial buffer) and
    store the serial data in µC RAM.

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