microblaze Serial port learning ·2

Serial initialization function 1int XUartLite_Initialize(XUartLite *InstancePtr, u16 DeviceId)

int XUartLite_Initialize(XUartLite *InstancePtr, u16 DeviceId){	XUartLite_Config *ConfigPtr;	Xil_AssertNonvoid(InstancePtr != NULL);	ConfigPtr = XUartLite_LookupConfig(DeviceId);	if (ConfigPtr == (XUartLite_Config *)NULL) {		return XST_DEVICE_NOT_FOUND;	}	return XUartLite_CfgInitialize(InstancePtr, ConfigPtr,					ConfigPtr->RegBaseAddr);}

##1 Serial initialization XUartLite_Config *ConfigPtr;

typedef struct {	u16 DeviceId;		/**< Unique ID  of device */	UINTPTR RegBaseAddr;	/**< Register base address */	u32 BaudRate;		/**< Fixed baud rate */	u8  UseParity;		/**< Parity generator enabled when TRUE */	u8  ParityOdd;		/**< Parity generated is odd when TRUE, even					when FALSE */	u8  DataBits;		/**< Fixed data bits */} XUartLite_Config;

ConfigPtr Is a pointer to a structure , This structure contains some parameters of serial port configuration , It should be noted that .MDM Some parameters of the serial port cannot be modified at the register level . Therefore, it is necessary to instantiate the hardware engineering . Set it up

2 Xil_AssertNonvoid(InstancePtr != NULL);

xlinx The assertion function of , Used to check the validity of parameter input , Guess it was redirected assert Output , This will be studied later . It does not affect the overall logical implementation .

3 ConfigPtr = XUartLite_LookupConfig(DeviceId);

XUartLite_Config *XUartLite_LookupConfig(u16 DeviceId){	XUartLite_Config *CfgPtr = NULL;	u32 Index;	for (Index=0; Index < XPAR_XUARTLITE_NUM_INSTANCES; Index++) {		if (XUartLite_ConfigTable[Index].DeviceId == DeviceId) {			CfgPtr = &XUartLite_ConfigTable[Index];			break;		}	}	return CfgPtr;}

The control vector is assigned in this function .
First initialize the null pointer , Then check the peripherals ID, And then through IC Inquire about , take XUartLite_ConfigTable The parameters in are passed to XUartLite_Configptr.XUartLite_ConfigTable The structure and CfgPtr The structure of is exactly the same .XUartLite_ConfigTable By vitis Automatically generated parameter configuration file ,XUartLite_ConfigTable The essence is a structural constant , All the internal parameters are defined by macros , The specific parameters are saved in xparameter in .
If you enter DeviceID illegal , Then the function will return a null pointer , Causes configuration failure .

4 return XUartLite_CfgInitialize(InstancePtr, ConfigPtr,ConfigPtr->RegBaseAddr);

int XUartLite_CfgInitialize(XUartLite *InstancePtr, XUartLite_Config *Config,				UINTPTR EffectiveAddr){	(void) Config;	/*	 * Assert validates the input arguments	 */	Xil_AssertNonvoid(InstancePtr != NULL);	/*	 * Set some default values, including setting the callback	 * handlers to stubs.	 */	InstancePtr->SendBuffer.NextBytePtr = NULL;	InstancePtr->SendBuffer.RemainingBytes = 0;	InstancePtr->SendBuffer.RequestedBytes = 0;	InstancePtr->ReceiveBuffer.NextBytePtr = NULL;	InstancePtr->ReceiveBuffer.RemainingBytes = 0;	InstancePtr->ReceiveBuffer.RequestedBytes = 0;	InstancePtr->IsReady = XIL_COMPONENT_IS_READY;#if (XPAR_XUARTLITE_USE_DCR_BRIDGE != 0)	InstancePtr->RegBaseAddress = ((EffectiveAddr >> 2)) & 0xFFF;#else	InstancePtr->RegBaseAddress = EffectiveAddr;#endif	InstancePtr->RecvHandler = StubHandler;	InstancePtr->SendHandler = StubHandler;	/* Write to the control register to disable the interrupts, don't	 * reset the FIFOs are the user may want the data that's present	 */	XUartLite_WriteReg(InstancePtr->RegBaseAddress,				XUL_CONTROL_REG_OFFSET, 0);	/*	 * Clear the statistics for this driver	 */	XUartLite_ClearStats(InstancePtr);	return XST_SUCCESS;}

The parameter passed in is a peripheral pointer , Peripheral configuration parameter pointer , Starting address of peripheral register . First of all, I will introduce Config Struct pointer cast to typeless （ I don't understand it here , Why do I have to do this ？）

Assign initial values to some variables in the external structure
about XPAR_XUARTLITE_USE_DCR_BRIDGE I found the understanding of this Xlinx A piece of file .

On-Chip Periphaeral Bus (OPB)

**device control register (DCR) **

You can see that there are many different ways to access peripheral registers , The article mentioned a kind of CPU-OPB Bridge Road .
Dig a hole in this place first , We will study the implementation details and differences later .

5 XUartLite_WriteReg(BaseAddress, RegOffset, Data)

#define XUartLite_WriteReg(BaseAddress, RegOffset, Data)
XUartLite_Out32((BaseAddress) + (RegOffset), (u32)(Data))
Then follow the configuration , Write address + Address offset + data

Then clear the peripheral Stats reg sign , So far, initialization is complete .