RISC-V MCU CH32V103啟動檔案分析
阿新 • • 發佈：2021-08-15
啟動檔案由組合語言編寫，是系統上電覆位後第一個執行的程式。主要執行以下內容：
- 初始化gp(global pointer)全域性指標暫存器、sp(stack pointer)堆疊指標暫存器
- 將data資料從flash中載入至RAM中
- 清空bss段資料
- 初始化中斷向量表
- 配置系統時鐘
- 從Machine模式切換到User模式，進入main函式執行
CH32V103啟動檔案如下：
/********************************** (C) COPYRIGHT ******************************* * File Name : startup_ch32v10x.s * Author : WCH * Version : V1.0.0 * Date : 2020/04/30 * Description : CH32V10x vector table for eclipse toolchain. *******************************************************************************/ .section .init,"ax",@progbits /* 宣告section 為 .init */ .global _start /* 指明標籤_start的屬性為全域性性的 */ .align 1 _start: /* 標籤_start處 */ j handle_reset /* 跳轉至 handle_reset處 */ .word 0x00000013 /* 核心設計需要，不用關注 */ .word 0x00000013 .word 0x00000013 .word 0x00000013 .word 0x00000013 .word 0x00000013 .word 0x00000013 .word 0x00000013 .word 0x00000013 .word 0x00000013 .word 0x00000013 .word 0x00000013 .word 0x00100073 .section .vector,"ax",@progbits .align 1 _vector_base: /* 中斷向量表 */ .option norvc; j _start .word 0 j NMI_Handler /* NMI Handler */ j HardFault_Handler /* Hard Fault Handler */ .word 0 .word 0 .word 0 .word 0 .word 0 .word 0 .word 0 .word 0 j SysTick_Handler /* SysTick Handler */ .word 0 j SW_handler /* SW Handler */ .word 0 /* External Interrupts */ j WWDG_IRQHandler /* Window Watchdog */ j PVD_IRQHandler /* PVD through EXTI Line detect */ j TAMPER_IRQHandler /* TAMPER */ j RTC_IRQHandler /* RTC */ j FLASH_IRQHandler /* Flash */ j RCC_IRQHandler /* RCC */ j EXTI0_IRQHandler /* EXTI Line 0 */ j EXTI1_IRQHandler /* EXTI Line 1 */ j EXTI2_IRQHandler /* EXTI Line 2 */ j EXTI3_IRQHandler /* EXTI Line 3 */ j EXTI4_IRQHandler /* EXTI Line 4 */ j DMA1_Channel1_IRQHandler /* DMA1 Channel 1 */ j DMA1_Channel2_IRQHandler /* DMA1 Channel 2 */ j DMA1_Channel3_IRQHandler /* DMA1 Channel 3 */ j DMA1_Channel4_IRQHandler /* DMA1 Channel 4 */ j DMA1_Channel5_IRQHandler /* DMA1 Channel 5 */ j DMA1_Channel6_IRQHandler /* DMA1 Channel 6 */ j DMA1_Channel7_IRQHandler /* DMA1 Channel 7 */ j ADC1_2_IRQHandler /* ADC1_2 */ .word 0 .word 0 .word 0 .word 0 j EXTI9_5_IRQHandler /* EXTI Line 9..5 */ j TIM1_BRK_IRQHandler /* TIM1 Break */ j TIM1_UP_IRQHandler /* TIM1 Update */ j TIM1_TRG_COM_IRQHandler /* TIM1 Trigger and Commutation */ j TIM1_CC_IRQHandler /* TIM1 Capture Compare */ j TIM2_IRQHandler /* TIM2 */ j TIM3_IRQHandler /* TIM3 */ j TIM4_IRQHandler /* TIM4 */ j I2C1_EV_IRQHandler /* I2C1 Event */ j I2C1_ER_IRQHandler /* I2C1 Error */ j I2C2_EV_IRQHandler /* I2C2 Event */ j I2C2_ER_IRQHandler /* I2C2 Error */ j SPI1_IRQHandler /* SPI1 */ j SPI2_IRQHandler /* SPI2 */ j USART1_IRQHandler /* USART1 */ j USART2_IRQHandler /* USART2 */ j USART3_IRQHandler /* USART3 */ j EXTI15_10_IRQHandler /* EXTI Line 15..10 */ j RTCAlarm_IRQHandler /* RTC Alarm through EXTI Line */ j USBWakeUp_IRQHandler /* USB Wakeup from suspend */ j USBHD_IRQHandler /* USBHD */ .option rvc; .section .text. , "ax", @progbits /* 中斷服務程式弱定義 */ .weak NMI_Handler .weak HardFault_Handler .weak SysTick_Handler .weak SW_handler .weak WWDG_IRQHandler .weak PVD_IRQHandler .weak TAMPER_IRQHandler .weak RTC_IRQHandler .weak FLASH_IRQHandler .weak RCC_IRQHandler .weak EXTI0_IRQHandler .weak EXTI1_IRQHandler .weak EXTI2_IRQHandler .weak EXTI3_IRQHandler .weak EXTI4_IRQHandler .weak DMA1_Channel1_IRQHandler .weak DMA1_Channel2_IRQHandler .weak DMA1_Channel3_IRQHandler .weak DMA1_Channel4_IRQHandler .weak DMA1_Channel5_IRQHandler .weak DMA1_Channel6_IRQHandler .weak DMA1_Channel7_IRQHandler .weak ADC1_2_IRQHandler .weak EXTI9_5_IRQHandler .weak TIM1_BRK_IRQHandler .weak TIM1_UP_IRQHandler .weak TIM1_TRG_COM_IRQHandler .weak TIM1_CC_IRQHandler .weak TIM2_IRQHandler .weak TIM3_IRQHandler .weak TIM4_IRQHandler .weak I2C1_EV_IRQHandler .weak I2C1_ER_IRQHandler .weak I2C2_EV_IRQHandler .weak I2C2_ER_IRQHandler .weak SPI1_IRQHandler .weak SPI2_IRQHandler .weak USART1_IRQHandler .weak USART2_IRQHandler .weak USART3_IRQHandler .weak EXTI15_10_IRQHandler .weak RTCAlarm_IRQHandler .weak USBWakeUp_IRQHandler .weak USBHD_IRQHandler .section .text.handle_reset,"ax",@progbits .weak handle_reset .align 1 handle_reset: /* handle_reset起始位置 */ .option push .option norelax la gp, __global_pointer$ /* 將ld檔案中的標籤__global_pointer所處的地址值賦給gp暫存器 */ .option pop 1: la sp, _eusrstack /* 將ld檔案中的標籤_eusrstack所處的地址值賦給sp暫存器 */ 2: /* Load data section from flash to RAM */ la a0, _data_lma la a1, _data_vma la a2, _edata bgeu a1, a2, 2f 1: lw t0, (a0) sw t0, (a1) addi a0, a0, 4 addi a1, a1, 4 bltu a1, a2, 1b 2: /* clear bss section */ la a0, _sbss la a1, _ebss bgeu a0, a1, 2f 1: sw zero, (a0) addi a0, a0, 4 bltu a0, a1, 1b 2: /* enable all interrupt */ /* csrs csrw 功能相同，根據暫存器中每個為1的位，把CSR暫存器對應位置位 */ li t0, 0x88 csrs mstatus, t0 /* 機器模式狀態暫存器mstatus賦值為0x88，開啟所有中斷，設定MPP值為00 */ la t0, _vector_base ori t0, t0, 1 csrw mtvec, t0 /* 將中斷向量表的首地址賦值給mtvec暫存器（中斷髮生時PC的地址） */ jal SystemInit /* 設定MCU系統時鐘 */ la t0, main csrw mepc, t0 mret /* mret返回指令(M模式特有的指令)，呼叫該指令會進行如下操作： - 將PC指標設定為mepc的值 - 將mstatus的MPIE域複製到MIE來恢復之前的中斷使能 - 將許可權模式設定為mstatus的MPP域中的值。 晶片上電預設進入的是機器模式，通過將mstatus中的MPP值設定為00（00: User, 01: Supervisor, 11: Machine）， 並將main函式的地址賦值給mepc，呼叫mret，使得使用者在進入main函式執行時，晶片由機器模式切換為使用者模式。 */