usart1_tx_rx.zip_USART1-TX_USART1_RX_usart him tx rx_usart1_tx_串

/** ****************************************************************************** * @file system_stm32f4xx.c * @author MCD Application Team * @version V1.3.0 modified by Keil for MDK-ARM V5.0 * @date 08-November-2013 * @brief CMSIS Cortex-M4 Device Peripheral Access Layer System Source File. * This file contains the system clock configuration for STM32F4xx devices. * * 1. This file provides two functions and one global variable to be called from * user application: * - SystemInit(): Setups the system clock (System clock source, PLL Multiplier * and Divider factors, AHB/APBx prescalers and Flash settings), * depending on the configuration made in the clock xls tool. * This function is called at startup just after reset and * before branch to main program. This call is made inside * the "startup_stm32f4xx.s" file. * * - SystemCoreClock variable: Contains the core clock (HCLK), it can be used * by the user application to setup the SysTick * timer or configure other parameters. * * - SystemCoreClockUpdate(): Updates the variable SystemCoreClock and must * be called whenever the core clock is changed * during program execution. * * 2. After each device reset the HSI (16 MHz) is used as system clock source. * Then SystemInit() function is called, in "startup_stm32f4xx.s" file, to * configure the system clock before to branch to main program. * * 3. If the system clock source selected by user fails to startup, the SystemInit() * function will do nothing and HSI still used as system clock source. User can * add some code to deal with this issue inside the SetSysClock() function. * * 4. The default value of HSE crystal is set to 25MHz, refer to "HSE_VALUE" define * in "stm32f4xx.h" file. When HSE is used as system clock source, directly or * through PLL, and you are using different crystal you have to adapt the HSE * value to your own configuration. * * 5. This file configures the system clock as follows: *============================================================================= *============================================================================= * Supported STM32F40xxx/41xxx devices *----------------------------------------------------------------------------- * System Clock source | PLL (HSE) *----------------------------------------------------------------------------- * SYSCLK(Hz) | 168000000 *----------------------------------------------------------------------------- * HCLK(Hz) | 168000000 *----------------------------------------------------------------------------- * AHB Prescaler | 1 *----------------------------------------------------------------------------- * APB1 Prescaler | 4 *----------------------------------------------------------------------------- * APB2 Prescaler | 2 *----------------------------------------------------------------------------- * HSE Frequency(Hz) | 25000000 *----------------------------------------------------------------------------- * PLL_M | 25 *----------------------------------------------------------------------------- * PLL_N | 336 *----------------------------------------------------------------------------- * PLL_P | 2 *----------------------------------------------------------------------------- * PLL_Q | 7 *----------------------------------------------------------------------------- * PLLI2S_N | NA *----------------------------------------------------------------------------- * PLLI2S_R | NA *----------------------------------------------------------------------------- * I2S input clock | NA *----------------------------------------------------------------------------- * VDD(V) | 3.3 *----------------------------------------------------------------------------- * Main regulator output voltage | Scale1 mode *----------------------------------------------------------------------------- * Flash Latency(WS) | 5 *----------------------------------------------------------------------------- * Prefetch Buffer | ON *----------------------------------------------------------------------------- * Instruction cache | ON *----------------------------------------------------------------------------- * Data cache | ON *----------------------------------------------------------------------------- * Require 48MHz for USB OTG FS, | Disabled * SDIO and RNG clock | *----------------------------------------------------------------------------- *============================================================================= *============================================================================= * Supported STM32F42xxx/43xxx devices *----------------------------------------------------------------------------- * System Clock source | PLL (HSE) *----------------------------------------------------------------------------- * SYSCLK(Hz) | 180000000 *----------------------------------------------------------------------------- * HCLK(Hz) | 180000000 *----------------------------------------------------------------------------- * AHB Prescaler | 1 *----------------------------------------------------------------------------- * APB1 Prescaler | 4 *----------------------------------------------------------------------------- * APB2 Prescaler | 2 *----------------------------------------------------------------------------- * HSE Frequency(Hz) | 25000000 *----------------------------------------------------------------------------- * PLL_M | 25 *----------------------------------------------------------------------------- * PLL_N | 360 *----------------------------------------------------------------------------- * PLL_P | 2 *----------------------------------------------------------------------------- * PLL_Q | 7 *----------------------------------------------------------------------------- * PLLI2S_N | NA *----------------------------------------------------------------------------- * PLLI2S_R | NA *----------------------------------------------------------------------------- * I2S input clock | NA *----------------------------------------------------------------------------- * VDD(V)