網(wǎng)站改版影響seo嗎,wordpress 購(gòu)物商城,wordpress 快速建站,溫州市網(wǎng)站想要搞清這個(gè)問(wèn)題#xff0c;需要重點(diǎn)研究startup_cm.s文件。啟動(dòng)時(shí)#xff0c;RAM數(shù)據(jù)的初始化主要包括兩個(gè)過(guò)程#xff1a;RAM區(qū)域初始化#xff08;數(shù)據(jù)清0#xff09;#xff1b;有初始值的變量需要從flash中加載到ram中。RAM區(qū)域初始化這一段代碼由匯編實(shí)現(xiàn)#xf…想要搞清這個(gè)問(wèn)題需要重點(diǎn)研究startup_cm.s文件。啟動(dòng)時(shí)RAM數(shù)據(jù)的初始化主要包括兩個(gè)過(guò)程RAM區(qū)域初始化數(shù)據(jù)清0有初始值的變量需要從flash中加載到ram中。RAM區(qū)域初始化這一段代碼由匯編實(shí)現(xiàn)在startup_cm.s中主要由DTCM_Init和RamInit實(shí)現(xiàn)的貼一段DTCM_Init的代碼DTCM_Init:/* Initialize DTCM ECC */LDR R0, __DTCM_INITCMP R0, #0/* Skip if __DTCM_INIT is not set */beq DTCM_LOOP_ENDLDR R1, __INT_DTCM_STARTLDR R2, __INT_DTCM_ENDSUBS R2, R1SUBS R2, #1BLE DTCM_LOOP_ENDMOVS R0, #0MOVS R3, #0DTCM_LOOP:STM R1!, {R0, R3}SUBS R2, #8BGE DTCM_LOOPDTCM_LOOP_END:加載變量在startup_cm.s中有個(gè)函數(shù)_DATA_INIT通過(guò)該函數(shù)跳轉(zhuǎn)到C代碼startup.c由init_data_bss這個(gè)函數(shù)實(shí)現(xiàn)。分析init_data_bss的代碼可以發(fā)現(xiàn)__INIT_TABLE作為.init_table起始地址的標(biāo)簽會(huì)被強(qiáng)轉(zhuǎn)為Sys_CopyLayoutType *結(jié)構(gòu)體指針typedef struct{uint32 * ram_start; /*! Start address of section in RAM */uint32 * rom_start; /*! Start address of section in ROM */uint32 * rom_end; /*! End address of section in ROM */} Sys_CopyLayoutType;然后訪問(wèn)該結(jié)構(gòu)體的成員就得到了相應(yīng)區(qū)域的ram起始地址rom起始地址rom結(jié)束地址從而實(shí)現(xiàn)數(shù)據(jù)從flash加載到ram中。最后貼一下__INIT_TABLE可以發(fā)現(xiàn)每三行正好對(duì)應(yīng)結(jié)構(gòu)體的3個(gè)成員__INIT_TABLEDCD 9DCD rwBlock$$BaseDCD cacheable_data_init$$BaseDCD cacheable_data_init$$LimitDCD rwMcalDataBlock$$BaseDCD cacheable_mcal_data_init$$BaseDCD cacheable_mcal_data_init$$LimitDCD ramCodeBlock$$BaseDCD cacheable_code_init$$BaseDCD cacheable_code_init$$LimitDCD dataNcBlock$$BaseDCD non_cacheable_data_init$$BaseDCD non_cacheable_data_init$$LimitDCD constNcBlock$$BaseDCD non_cacheable_const_init$$BaseDCD non_cacheable_const_init$$LimitDCD dataShBlock$$Base#if (!defined(CORE0) defined(MULTIPLE_IMAGE))DCD 0DCD 0#elseDCD shareable_data_init$$BaseDCD shareable_data_init$$Limit#endifDCD intcVectorBlock$$BaseDCD interrupt_vector_init$$BaseDCD interrupt_vector_init$$LimitDCD dataDtcmBlock$$BaseDCD dtcmDataBlock_init$$BaseDCD dtcmDataBlock_init$$LimitDCD textItcmBlock$$BaseDCD itcmCodeBlock_init$$BaseDCD itcmCodeBlock_init$$Limit__INIT_TABLE_END