RCC configuration Master

void RCC_Configuration(void)//72MHz(Master module)
{
	RCC_DeInit();
	RCC_ClearFlag();
	RCC_HSEConfig(RCC_HSE_ON);
	FLASH->ACR|=FLASH_Latency_2;
	FLASH->ACR|=FLASH_PrefetchBuffer_Enable;
	RCC_PLLConfig(RCC_PLLSource_HSE_Div1,RCC_PLLMul_9);				
	RCC_PCLK1Config(RCC_HCLK_Div2);
	RCC_PCLK2Config(RCC_HCLK_Div1);
	RCC_ADCCLKConfig(RCC_PCLK2_Div6);
	RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
	RCC_PLLCmd(ENABLE);
	while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY)==RESET);
	while(RCC_WaitForHSEStartUp()==ERROR);		 
} 

void RCC_Configuration(void)//8MHz(Master module)
{
	RCC_DeInit();
	RCC_ClearFlag();
	RCC_HSEConfig(RCC_HSE_ON);
	FLASH->ACR|=FLASH_Latency_2;
	FLASH->ACR|=FLASH_PrefetchBuffer_Enable;
	RCC_PLLConfig(RCC_PLLSource_HSE_Div2,RCC_PLLMul_2);				
	RCC_PCLK1Config(RCC_HCLK_Div2);
	RCC_PCLK2Config(RCC_HCLK_Div1);
	RCC_ADCCLKConfig(RCC_PCLK2_Div6);
	RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
	RCC_PLLCmd(ENABLE);
	while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY)==RESET);
	while(RCC_WaitForHSEStartUp()==ERROR);		 
}  


USART1 Configuration (Master)

 void USART_Configuration(void)
{
	
    USART_InitTypeDef USART_InitStruct;
    USART_InitStruct.USART_BaudRate = 115200;
    USART_InitStruct.USART_WordLength = USART_WordLength_8b;
    USART_InitStruct.USART_StopBits = USART_StopBits_1;
    USART_InitStruct.USART_Parity = USART_Parity_No;
    USART_InitStruct.USART_Mode = USART_Mode_Tx|USART_Mode_Rx;
    USART_InitStruct.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
	
    USART_Init(USART1,&USART_InitStruct);
    USART_ITConfig(USART1, USART_IT_RXNE,ENABLE);
    USART_Cmd(USART1,ENABLE);
    // the alternate function and NVIC thing i have done 	

}



RCC configuration (Slave) 

#define __RCC_CFGR_VAL             0x00038402
#define __RCC_CR_VAL               0x01010082


void RCC_Configuration(void)
{
  RCC->CFGR = __RCC_CFGR_VAL;                        // 
  RCC->CR   = __RCC_CR_VAL;                          // set clock control register

  if (__RCC_CR_VAL & RCC_CR_HSION) {                 // if HSI enabled
    while ((RCC->CR & RCC_CR_HSIRDY) == 0);          // Wait for HSIRDY = 1 (HSI is ready)
  }

  if (__RCC_CR_VAL & RCC_CR_HSEON) {                 // if HSE enabled
    while ((RCC->CR & RCC_CR_HSERDY) == 0);          // Wait for HSERDY = 1 (HSE is ready)
  }

  if (__RCC_CR_VAL & RCC_CR_PLLON) {                 // if PLL enabled
    while ((RCC->CR & RCC_CR_PLLRDY) == 0);          // Wait for PLLRDY = 1 (PLL is ready)
  }

  /* Wait till SYSCLK is stabilized (depending on selected clock) */
  while ((RCC->CFGR & RCC_CFGR_SWS) != ((__RCC_CFGR_VAL<<2) & RCC_CFGR_SWS));
}


USART1 Configuration (Slave)

void USART1_CONFIGURATION()
{
	RCC->APB2ENR |= RCC_APB2ENR_AFIOEN;                     // enable clock for Alternate Function
    	AFIO->MAPR  &= ~(1 << 2);                              // clear USART1 remap
	GPIOA->CRH &= 0xFFFFF00F;
	GPIOA->CRH |= 0x400;
	GPIOA->CRH |= 0xB0;
    	RCC->APB2ENR |= RCC_APB2ENR_USART1EN;                   // enable clock for USART1    
    	USART1->BRR  = 0x45;//0x68;//0xD0;//0x271;//0xD0;//0X68;//0x8A;//0x1D4C;//0x271;//0x1D4C; //__USART_BRR(__PCLK2, __USART1_BAUDRATE); // set baudrate
    	USART1->CR1  = __USART1_DATABITS;                       // set Data bits
    	USART1->CR2  = __USART1_STOPBITS;                       // set Stop bits
    	USART1->CR1 |= __USART1_PARITY;                         // set Parity
    	USART1->CR3  = __USART1_FLOWCTRL;                       // Set Flow Control
    	USART1->CR1 |= (USART_CR1_TE | USART_CR1_RE);           // RX, TX enable
      	USART1->CR1 |= USART_FLAG_RXNE;
      	USART1->CR2 |= __USART1_CR2;
      	USART1->CR3 |= __USART1_CR3;  
	USART1->CR1 |= 0x00002000;
     	NVIC->ISER[1] |= (1 << (0x25 & 0x1F));   // enable interrupt

}