Section VI UART of zynq

ZYNQ Of UART

1 UART Characteristics

ZYNQ The serial port module is a full duplex asynchronous receiver and transmitter , Support a wide range of software programmable modules , Support programming to configure baud rate and data format , At the same time, it provides automatic parity check and error detection scheme , Besides , Also for APU Provides receive and send FIFO.

ZYNQ There are two UART device , It has the following characteristics ：

1. Programmable baud rate transmitter ;
2. 64 Bytes received and sent FIFO;
3. Data bits 6,7 perhaps 8 A bit ;
4. p. , accidentally , Space , Marked or not verified ;
5. 1,1.5 perhaps 2 Stop bits ;
6. Support verification , Frame and overrun error detection ;
7. Support automatic response , Local loop and remote loop channel modes ;
8. Support interrupt generation ;
9. stay EMIO On , A modem can be used to control the signal CTS,RTS,DSR,DTR,RI and DCD;

Its structural frame is shown in the figure 1 Shown ：

chart 1 UART The structure of

APB Interface ：

adopt APB Interface ,PS It can be done to UART Read and write the internal registers of the controller ;

Tx FIFO

Tx FIFO Used to save data from APB Interface write data , Until the transmitter module takes it out and sends it to the transmit shift register ,Tx FIFO Control the flow through the full and empty flags , Besides , You can also set Tx FIFO Trigger level of ;

Rx FIFO：

Rx FIFO Used to save data from the receive shift register ,Rx FIFO The full and empty flag of is used to receive data flow control , Besides , You can also set Rx FIFO Trigger level of ;

transmitter :

The transmitter takes out the transmitter FIFO Data in , And load it into the transmit shift register , Serialize parallel data ;

Receiver ：

UART Continuous sampling ua_rxd The signal , When a low level change is detected , Indicates the beginning of receiving data ;

Control and status module ：

The control register is used to enable , Disable and issue software resets to receiver and transmitter modules , You can also configure features such as receive timeout and send disconnection ; The mode register selects the clock through the baud rate generator , It is also responsible for selecting the length of bits of data sent and received , Parity bit and stop bit , You can also choose UART Working mode of , Include automatic responses , Local loop, remote loop, etc ;

Interrupt control ：

Through channel interrupt status register and channel status register , And the interrupt control module detects from other UART Module events ; By using the interrupt enable register and interrupt disable register , Enable or disable interrupts , The interrupt enable or disable status is reflected in the interrupt mask register ;

Baud rate generator ：

chart 2 The principle of baud rate generator is given , In the figure CD Is a bit field of the baud rate generator , Used to generate sample rate clock band_sample.

chart 2 Baud rate transmitter

The final baud rate generation mainly includes the following 3 A step ：

1. UART Clock selection , It can be directly UART Ref clock, It can also be done by bypass 8 frequency division , The setting is in uart.mode_reg0[0] In the middle of ;
2. Yes UART Divide the clock , produce band_sample The frequency calculation formula is as follows ：

baud_sample = sel_clk/CD

1. Yes baud_sample Divide the frequency again , produce Rx and Tx Baud rate , This step is done by setting BDIV Value completion , That is to say uart.Baud_rate_Divider_reg0[7：0] Set it up , Baud rate calculation formula is as follows ：

baud_rate = sel_clk/(CD*(BDIV + 1))

             UART Ref clock,CD and BDIV The value of determines UART Baud rate , If UART_Ref_Clk=50MHz,Uart_ref_clk/8=6.25MHz. chart 3 Indicates the corresponding to the typical baud rate CD and eBDIV value ;

chart 3 CD and eBDIV Corresponding baud rate

2 UART Using examples

Instance content ： Good configuration ZYNQ Of UART interrupt , Implement interrupt service function , The received data is passed in the receive interrupt UART Send it out ;

To configure UART The steps are as follows ：

1. adopt UART The peripherals of ID Find the corresponding peripheral information ;
2. fill UART Peripheral register base address and some related information ;
3. To configure UART Of course GIC interrupt ;
4. To configure UART Interrupt trigger mode （ Receive or send interrupt ）;
5. Set up UART Of FIFO Trigger level ;
6. Can make UART peripherals ;

To configure UART Of GIC The interrupt steps are as follows ：

1. Connect to hardware , Map the corresponding interrupt to GIC Interrupt request ;
2. find GIC interrupt , fill GIC Interrupt register base address and some related information ;
3. find UART Interrupt source , Fill in timer interrupt register base address and some related information ;
4. take UART The interrupt is mapped to the interrupt service function of the timer interrupt ;
5. Can make GIC interrupt ;
6. Enable the mapping of interrupt vector table and interrupt vector table ;

Program source code ：

//UART Of GIC initialization

void Init_Gic_Uart(void)

{

    XScuGic_Config *IntcConfig;

    //connect hardware

    Xil_ExceptionInit();

    Xil_ExceptionRegisterHandler(XIL_EXCEPTION_ID_INT,

                        (Xil_ExceptionHandler)XScuGic_InterruptHandler,

                        (void *)&Intc);

    //find XScuGic device

    IntcConfig = XScuGic_LookupConfig(INTC_DEVICE_ID);

    //config XScuGic data

    XScuGic_CfgInitialize(&Intc,IntcConfig,IntcConfig->CpuBaseAddress);

    //GIC Connect to handler function

  XScuGic_Connect(&Intc,UART_IRPT_INTR,(Xil_InterruptHandler)UartIntrHandler, (void *)&Uart);

    //enable XScuGic

    XScuGic_Enable(&Intc,UART_IRPT_INTR);

    //enable exception

    Xil_ExceptionEnable();

    Xil_ExceptionEnableMask(XIL_EXCEPTION_IRQ);

}

 

//UART initialization

void Init_Uart(void)

{

    XUartPs_Config * UartConfigPtr;

    //fined uart device

    UartConfigPtr = XUartPs_LookupConfig(UART_DEVICE_ID);

    //config XUartPs data

    XUartPs_CfgInitialize(&Uart,UartConfigPtr,UartConfigPtr->BaseAddress);

    //set uart mask

    XUartPs_SetInterruptMask(&Uart,XUARTPS_IXR_RXOVR);

    XUartPs_SetFifoThreshold(&Uart,10);

    //enable uart

    XUartPs_EnableUart(&Uart);

}

 

//UART Interrupt service function

void UartIntrHandler(void *CallBackRef)

{

    XUartPs *InstancePrt = (XUartPs *)CallBackRef;

    u32 IsrStatus;

    u32 ReceivedCount = 0;

    u32 CsrRegister;

    IsrStatus = XUartPs_ReadReg(InstancePrt->Config.BaseAddress,XUARTPS_IMR_OFFSET);

    IsrStatus &= XUartPs_ReadReg(InstancePrt->Config.BaseAddress,XUARTPS_ISR_OFFSET);

 

    if((IsrStatus & ((u32)XUARTPS_IXR_RXOVR | (u32)XUARTPS_IXR_RXEMPTY | (u32)XUARTPS_IXR_RXFULL)) != (u32)0)

    {

        CsrRegister = XUartPs_ReadReg(InstancePrt->Config.BaseAddress,XUARTPS_SR_OFFSET);

        while((CsrRegister & XUARTPS_SR_RXEMPTY) == (u32)0)

        {

XUartPs_WriteReg(InstancePrt->Config.BaseAddress,XUARTPS_FIFO_OFFSET,XUartPs_ReadReg(InstancePrt->Config.BaseAddress,XUARTPS_FIFO_OFFSET));

            ReceivedCount++;

            CsrRegister = XUartPs_ReadReg(InstancePrt->Config.BaseAddress,XUARTPS_SR_OFFSET);

        }

    }

//  printf("thistimeReceivedCount=%d\r\n",ReceivedCount);

XUartPs_WriteReg(InstancePrt->Config.BaseAddress,XUARTPS_ISR_OFFSET,IsrStatus);

}