100脚的STM32F407VE单片机使用FSMC扩展外部SRAM芯片IS62WV51216BLL

该SRAM芯片有A18~0共19根地址线，即2^19=524288个地址，有D15~0共16根数据线，因此位宽为16位，也就是2字节。总容量为524288×2=1048576字节=1MB。

连线：

A0~13接PC0~13，由于PC14和PC15接了LSE晶振，所以把A14~15接到PA0~1上，这16位地址手动生成。注意：SRAM不可使用混合模式，A15~0不能和D15~0接到一起。

A16~18接FSMC的PD11~13，这三位地址由FSMC自动生成。

D0~1接PD14~15，D2~3接PD0~1，D4~12接PE7~15，D13~15接PD8~10。

片选信号NE3（E=Enable）接到FSMC上的NE1：PD7。注意微雪IS62WV51216BLL SRAM板上虽然有NE2~3、CS1~3五个片选引脚，但其实只有NE3上面焊接了电阻连接到了芯片上（如下图所示）。

NOE（OE=Output Enable，前缀N表示低电平有效）接PD4。NWE（WE=Write Enable）接PD5。NBL0（BL=Byte Lane）接PE0，NBL1接PE1。

最后把电源引脚VCC和GND接上，电压为3.3V。

【程序】

#include <stdio.h>#include <stm32f4xx.h>// 单片机上的片选信号NE1(PD7)必须接到SRAM板上的NE3引脚上, 因为其他引脚都没有焊接电阻！！！int fputc(int ch, FILE *fp){if (fp == stdout){if (ch == '\n'){while ((USART1->SR & USART_SR_TXE) == 0);USART1->DR = '\r';}while ((USART1->SR & USART_SR_TXE) == 0);USART1->DR = ch;}return ch;}// addr的范围: 0~524287uint16_t read(uint32_t addr){GPIOC->ODR = addr & 0x3fff;GPIOA->ODR = (addr >> 14) & 0x03;return *(volatile uint16_t *)(0x60000000 | (addr << 1));}void write(uint32_t addr, uint16_t value){GPIOC->ODR = addr & 0x3fff;GPIOA->ODR = (addr >> 14) & 0x03;*(volatile uint16_t *)(0x60000000 | (addr << 1)) = value;}// 8位访存测试void test8(void){volatile uint8_t *const arr = (volatile uint8_t *)0x60000000;uint8_t i;for (i = 0; i < 20; i++){GPIOC->ODR = i >> 1; // 地址引脚arr[i] = 3 * i;}for (i = 0; i < 20; i++){GPIOC->ODR = i >> 1;printf("%d ", arr[i]);}printf("\n");}// 16位访存测试void test16(void){uint32_t i;for (i = 0; i <= 524287; i++)write(i, i / 10);for (i = 0; i <= 100; i++){printf("[%d]%d ", i, read(i));if (i % 5 == 4)printf("\n");}for (i = 523500; i <= 524287; i++){printf("[%d]%d ", i, read(i));if (i % 5 == 4)printf("\n");}printf("\n");}int main(void){RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN | RCC_AHB1ENR_GPIOCEN | RCC_AHB1ENR_GPIODEN | RCC_AHB1ENR_GPIOEEN;RCC->AHB3ENR = RCC_AHB3ENR_FSMCEN;RCC->APB2ENR = RCC_APB2ENR_USART1EN;GPIOA->AFR[1] = 0x00000070; // PA9为USART1的发送端口GPIOA->MODER |= 0x00080005; // PA0~1设为输出, PA9设为复用GPIOC->MODER = 0x05555555; // PC0~13设为输出// PD, PE上所有与FSMC有关的引脚全部设为复用GPIOD->AFR[0] = 0xc0cc00cc; // FSMC为AF12GPIOD->AFR[1] = 0xcccccccc;GPIOD->MODER = 0xaaaa8a0a;GPIOE->AFR[0] = 0xc00000cc;GPIOE->AFR[1] = 0xcccccccc;GPIOE->MODER = 0xaaaa800a;FSMC_Bank1->BTCR[0] &= ~(FSMC_BCR1_WAITEN | FSMC_BCR1_FACCEN | FSMC_BCR1_MTYP | FSMC_BCR1_MUXEN); // MTYPE=00(SRAM), MUXEN=0//FSMC_Bank1->BTCR[0] |= FSMC_BCR1_MTYP_0; // MTYPE=01(PSRAM)FSMC_Bank1->BTCR[1] = 0x313; // DATAST=3, ADDHLD=1, ADDSET=3USART1->BRR = SystemCoreClock / 115200;USART1->CR1 = USART_CR1_UE | USART_CR1_TE;test8();test16();while (1);}

【程序运行结果】

0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57[0]0 [1]0 [2]0 [3]0 [4]0[5]0 [6]0 [7]0 [8]0 [9]0[10]1 [11]1 [12]1 [13]1 [14]1[15]1 [16]1 [17]1 [18]1 [19]1[20]2 [21]2 [22]2 [23]2 [24]2[25]2 [26]2 [27]2 [28]2 [29]2[30]3 [31]3 [32]3 [33]3 [34]3[35]3 [36]3 [37]3 [38]3 [39]3[40]4 [41]4 [42]4 [43]4 [44]4[45]4 [46]4 [47]4 [48]4 [49]4[50]5 [51]5 [52]5 [53]5 [54]5[55]5 [56]5 [57]5 [58]5 [59]5[60]6 [61]6 [62]6 [63]6 [64]6[65]6 [66]6 [67]6 [68]6 [69]6[70]7 [71]7 [72]7 [73]7 [74]7[75]7 [76]7 [77]7 [78]7 [79]7[80]8 [81]8 [82]8 [83]8 [84]8[85]8 [86]8 [87]8 [88]8 [89]8[90]9 [91]9 [92]9 [93]9 [94]9[95]9 [96]9 [97]9 [98]9 [99]9[100]10 [523500]52350 [523501]52350 [523502]52350 [523503]52350 [523504]52350[523505]52350 [523506]52350 [523507]52350 [523508]52350 [523509]52350[523510]52351 [523511]52351 [523512]52351 [523513]52351 [523514]52351[523515]52351 [523516]52351 [523517]52351 [523518]52351 [523519]52351[523520]52352 [523521]52352 [523522]52352 [523523]52352 [523524]52352[523525]52352 [523526]52352 [523527]52352 [523528]52352 [523529]52352[523530]52353 [523531]52353 [523532]52353 [523533]52353 [523534]52353[523535]52353 [523536]52353 [523537]52353 [523538]52353 [523539]52353[523540]52354 [523541]52354 [523542]52354 [523543]52354 [523544]52354[523545]52354 [523546]52354 [523547]52354 [523548]52354 [523549]52354[523550]52355 [523551]52355 [523552]52355 [523553]52355 [523554]52355[523555]52355 [523556]52355 [523557]52355 [523558]52355 [523559]52355[523560]52356 [523561]52356 [523562]52356 [523563]52356 [523564]52356[523565]52356 [523566]52356 [523567]52356 [523568]52356 [523569]52356[523570]52357 [523571]52357 [523572]52357 [523573]52357 [523574]52357[523575]52357 [523576]52357 [523577]52357 [523578]52357 [523579]52357[523580]52358 [523581]52358 [523582]52358 [523583]52358 [523584]52358[523585]52358 [523586]52358 [523587]52358 [523588]52358 [523589]52358[523590]52359 [523591]52359 [523592]52359 [523593]52359 [523594]52359[523595]52359 [523596]52359 [523597]52359 [523598]52359 [523599]52359[523600]52360 [523601]52360 [523602]52360 [523603]52360 [523604]52360[523605]52360 [523606]52360 [523607]52360 [523608]52360 [523609]52360[523610]52361 [523611]52361 [523612]52361 [523613]52361 [523614]52361[523615]52361 [523616]52361 [523617]52361 [523618]52361 [523619]52361[523620]52362 [523621]52362 [523622]52362 [523623]52362 [523624]52362[523625]52362 [523626]52362 [523627]52362 [523628]52362 [523629]52362[523630]52363 [523631]52363 [523632]52363 [523633]52363 [523634]52363[523635]52363 [523636]52363 [523637]52363 [523638]52363 [523639]52363[523640]52364 [523641]52364 [523642]52364 [523643]52364 [523644]52364[523645]52364 [523646]52364 [523647]52364 [523648]52364 [523649]52364[523650]52365 [523651]52365 [523652]52365 [523653]52365 [523654]52365[523655]52365 [523656]52365 [523657]52365 [523658]52365 [523659]52365[523660]52366 [523661]52366 [523662]52366 [523663]52366 [523664]52366[523665]52366 [523666]52366 [523667]52366 [523668]52366 [523669]52366[523670]52367 [523671]52367 [523672]52367 [523673]52367 [523674]52367[523675]52367 [523676]52367 [523677]52367 [523678]52367 [523679]52367[523680]52368 [523681]52368 [523682]52368 [523683]52368 [523684]52368[523685]52368 [523686]52368 [523687]52368 [523688]52368 [523689]52368[523690]52369 [523691]52369 [523692]52369 [523693]52369 [523694]52369[523695]52369 [523696]52369 [523697]52369 [523698]52369 [523699]52369[523700]52370 [523701]52370 [523702]52370 [523703]52370 [523704]52370[523705]52370 [523706]52370 [523707]52370 [523708]52370 [523709]52370[523710]52371 [523711]52371 [523712]52371 [523713]52371 [523714]52371[523715]52371 [523716]52371 [523717]52371 [523718]52371 [523719]52371[523720]52372 [523721]52372 [523722]52372 [523723]52372 [523724]52372[523725]52372 [523726]52372 [523727]52372 [523728]52372 [523729]52372[523730]52373 [523731]52373 [523732]52373 [523733]52373 [523734]52373[523735]52373 [523736]52373 [523737]52373 [523738]52373 [523739]52373[523740]52374 [523741]52374 [523742]52374 [523743]52374 [523744]52374[523745]52374 [523746]52374 [523747]52374 [523748]52374 [523749]52374[523750]52375 [523751]52375 [523752]52375 [523753]52375 [523754]52375[523755]52375 [523756]52375 [523757]52375 [523758]52375 [523759]52375[523760]52376 [523761]52376 [523762]52376 [523763]52376 [523764]52376[523765]52376 [523766]52376 [523767]52376 [523768]52376 [523769]52376[523770]52377 [523771]52377 [523772]52377 [523773]52377 [523774]52377[523775]52377 [523776]52377 [523777]52377 [523778]52377 [523779]52377[523780]52378 [523781]52378 [523782]52378 [523783]52378 [523784]52378[523785]52378 [523786]52378 [523787]52378 [523788]52378 [523789]52378[523790]52379 [523791]52379 [523792]52379 [523793]52379 [523794]52379[523795]52379 [523796]52379 [523797]52379 [523798]52379 [523799]52379[523800]52380 [523801]52380 [523802]52380 [523803]52380 [523804]52380[523805]52380 [523806]52380 [523807]52380 [523808]52380 [523809]52380[523810]52381 [523811]52381 [523812]52381 [523813]52381 [523814]52381[523815]52381 [523816]52381 [523817]52381 [523818]52381 [523819]52381[523820]52382 [523821]52382 [523822]52382 [523823]52382 [523824]52382[523825]52382 [523826]52382 [523827]52382 [523828]52382 [523829]52382[523830]52383 [523831]52383 [523832]52383 [523833]52383 [523834]52383[523835]52383 [523836]52383 [523837]52383 [523838]52383 [523839]52383[523840]52384 [523841]52384 [523842]52384 [523843]52384 [523844]52384[523845]52384 [523846]52384 [523847]52384 [523848]52384 [523849]52384[523850]52385 [523851]52385 [523852]52385 [523853]52385 [523854]52385[523855]52385 [523856]52385 [523857]52385 [523858]52385 [523859]52385[523860]52386 [523861]52386 [523862]52386 [523863]52386 [523864]52386[523865]52386 [523866]52386 [523867]52386 [523868]52386 [523869]52386[523870]52387 [523871]52387 [523872]52387 [523873]52387 [523874]52387[523875]52387 [523876]52387 [523877]52387 [523878]52387 [523879]52387[523880]52388 [523881]52388 [523882]52388 [523883]52388 [523884]52388[523885]52388 [523886]52388 [523887]52388 [523888]52388 [523889]52388[523890]52389 [523891]52389 [523892]52389 [523893]52389 [523894]52389[523895]52389 [523896]52389 [523897]52389 [523898]52389 [523899]52389[523900]52390 [523901]52390 [523902]52390 [523903]52390 [523904]52390[523905]52390 [523906]52390 [523907]52390 [523908]52390 [523909]52390[523910]52391 [523911]52391 [523912]52391 [523913]52391 [523914]52391[523915]52391 [523916]52391 [523917]52391 [523918]52391 [523919]52391[523920]52392 [523921]52392 [523922]52392 [523923]52392 [523924]52392[523925]52392 [523926]52392 [523927]52392 [523928]52392 [523929]52392[523930]52393 [523931]52393 [523932]52393 [523933]52393 [523934]52393[523935]52393 [523936]52393 [523937]52393 [523938]52393 [523939]52393[523940]52394 [523941]52394 [523942]52394 [523943]52394 [523944]52394[523945]52394 [523946]52394 [523947]52394 [523948]52394 [523949]52394[523950]52395 [523951]52395 [523952]52395 [523953]52395 [523954]52395[523955]52395 [523956]52395 [523957]52395 [523958]52395 [523959]52395[523960]52396 [523961]52396 [523962]52396 [523963]52396 [523964]52396[523965]52396 [523966]52396 [523967]52396 [523968]52396 [523969]52396[523970]52397 [523971]52397 [523972]52397 [523973]52397 [523974]52397[523975]52397 [523976]52397 [523977]52397 [523978]52397 [523979]52397[523980]52398 [523981]52398 [523982]52398 [523983]52398 [523984]52398[523985]52398 [523986]52398 [523987]52398 [523988]52398 [523989]52398[523990]52399 [523991]52399 [523992]52399 [523993]52399 [523994]52399[523995]52399 [523996]52399 [523997]52399 [523998]52399 [523999]52399[524000]52400 [524001]52400 [524002]52400 [524003]52400 [524004]52400[524005]52400 [524006]52400 [524007]52400 [524008]52400 [524009]52400[524010]52401 [524011]52401 [524012]52401 [524013]52401 [524014]52401[524015]52401 [524016]52401 [524017]52401 [524018]52401 [524019]52401[524020]52402 [524021]52402 [524022]52402 [524023]52402 [524024]52402[524025]52402 [524026]52402 [524027]52402 [524028]52402 [524029]52402[524030]52403 [524031]52403 [524032]52403 [524033]52403 [524034]52403[524035]52403 [524036]52403 [524037]52403 [524038]52403 [524039]52403[524040]52404 [524041]52404 [524042]52404 [524043]52404 [524044]52404[524045]52404 [524046]52404 [524047]52404 [524048]52404 [524049]52404[524050]52405 [524051]52405 [524052]52405 [524053]52405 [524054]52405[524055]52405 [524056]52405 [524057]52405 [524058]52405 [524059]52405[524060]52406 [524061]52406 [524062]52406 [524063]52406 [524064]52406[524065]52406 [524066]52406 [524067]52406 [524068]52406 [524069]52406[524070]52407 [524071]52407 [524072]52407 [524073]52407 [524074]52407[524075]52407 [524076]52407 [524077]52407 [524078]52407 [524079]52407[524080]52408 [524081]52408 [524082]52408 [524083]52408 [524084]52408[524085]52408 [524086]52408 [524087]52408 [524088]52408 [524089]52408[524090]52409 [524091]52409 [524092]52409 [524093]52409 [524094]52409[524095]52409 [524096]52409 [524097]52409 [524098]52409 [524099]52409[524100]52410 [524101]52410 [524102]52410 [524103]52410 [524104]52410[524105]52410 [524106]52410 [524107]52410 [524108]52410 [524109]52410[524110]52411 [524111]52411 [524112]52411 [524113]52411 [524114]52411[524115]52411 [524116]52411 [524117]52411 [524118]52411 [524119]52411[524120]52412 [524121]52412 [524122]52412 [524123]52412 [524124]52412[524125]52412 [524126]52412 [524127]52412 [524128]52412 [524129]52412[524130]52413 [524131]52413 [524132]52413 [524133]52413 [524134]52413[524135]52413 [524136]52413 [524137]52413 [524138]52413 [524139]52413[524140]52414 [524141]52414 [524142]52414 [524143]52414 [524144]52414[524145]52414 [524146]52414 [524147]52414 [524148]52414 [524149]52414[524150]52415 [524151]52415 [524152]52415 [524153]52415 [524154]52415[524155]52415 [524156]52415 [524157]52415 [524158]52415 [524159]52415[524160]52416 [524161]52416 [524162]52416 [524163]52416 [524164]52416[524165]52416 [524166]52416 [524167]52416 [524168]52416 [524169]52416[524170]52417 [524171]52417 [524172]52417 [524173]52417 [524174]52417[524175]52417 [524176]52417 [524177]52417 [524178]52417 [524179]52417[524180]52418 [524181]52418 [524182]52418 [524183]52418 [524184]52418[524185]52418 [524186]52418 [524187]52418 [524188]52418 [524189]52418[524190]52419 [524191]52419 [524192]52419 [524193]52419 [524194]52419[524195]52419 [524196]52419 [524197]52419 [524198]52419 [524199]52419[524200]52420 [524201]52420 [524202]52420 [524203]52420 [524204]52420[524205]52420 [524206]52420 [524207]52420 [524208]52420 [524209]52420[524210]52421 [524211]52421 [524212]52421 [524213]52421 [524214]52421[524215]52421 [524216]52421 [524217]52421 [524218]52421 [524219]52421[524220]52422 [524221]52422 [524222]52422 [524223]52422 [524224]52422[524225]52422 [524226]52422 [524227]52422 [524228]52422 [524229]52422[524230]52423 [524231]52423 [524232]52423 [524233]52423 [524234]52423[524235]52423 [524236]52423 [524237]52423 [524238]52423 [524239]52423[524240]52424 [524241]52424 [524242]52424 [524243]52424 [524244]52424[524245]52424 [524246]52424 [524247]52424 [524248]52424 [524249]52424[524250]52425 [524251]52425 [524252]52425 [524253]52425 [524254]52425[524255]52425 [524256]52425 [524257]52425 [524258]52425 [524259]52425[524260]52426 [524261]52426 [524262]52426 [524263]52426 [524264]52426[524265]52426 [524266]52426 [524267]52426 [524268]52426 [524269]52426[524270]52427 [524271]52427 [524272]52427 [524273]52427 [524274]52427[524275]52427 [524276]52427 [524277]52427 [524278]52427 [524279]52427[524280]52428 [524281]52428 [524282]52428 [524283]52428 [524284]52428[524285]52428 [524286]52428 [524287]52428

在FSMC中共有4个Bank，其中第一个Bank专门用于访问NOR Flash和SRAM、PSRAM存储器，寻址空间为256MB。IS62WV51216BLL芯片属于SRAM存储器。地址、数据线混合模式（Multiplexed I/Os）通常只能用于NOR Flash存储器，不能用于SRAM存储器。所以，在程序中我们将MUXEN置0，关闭了混合模式。EXTMOD为0，不开启扩展模式。

Bank 2和Bank 3用于NAND Flash，Bank 4用于PC Card。

Bank 1的地址范围是0x60000000~0x6FFFFFFF，该Bank又分为4个Subbank，记为Bank1 - NOR/PSRAM 1~4，每个Subbank的寻址空间为64MB。但在100脚的芯片中，只有Bank1 - NOR/PSRAM 1可用，其片选端口为NE1(PD7），地址范围为0x60000000~0x63FFFFFF。地址的第27~26位决定Subbank，第25~0位由外部地址线决定。

由于该SRAM芯片每个地址访问的是两个字节的数据，而在STM32单片机中每个地址只允许访问1字节的数据，所以在访存时，STM32单片机先将第25~1位送到SRAM地址线上（对于该芯片来说，则是第20~1位），然后根据最后一位地址位决定NBL1~0引脚的电平。

Bank 1的每个Subbank都有3个寄存器：FSMC_BCRx，FSMC_BTRx，FSMC_BWTRx，其中x为1~4。只有选用了扩展模式（EXTMOD=1时），BWTRx寄存器才有效。BTCR[0]就是FSMC_BCR1寄存器，BTCR[1]为FSMC_BTR1，BTCR[2]为FSMC_BCR2，BTCR[3]为FSMC_BTR2，以此类推。

默认情况下，Subbank1是打开的（MBKEN=1），但存储器类型却是NOR Flash（MTYP=10），因此需要在程序中改成SRAM（MTYP=00），且还要将FACCEN置0（是否开启NOR Flash访问）。位宽默认就是16位（MWID=01），无需改动。由于SRAM上没有NWAIT引脚，因此还需把WAITEN置0。

还要注意的是，BCR寄存器中的第7位为保留位，必须要保持复位时的默认值，也就是1（而不是0）。

由于100脚的单片机里没有A15~0引脚，因此我们把它接到了PC0~13和PA0~1上，然后在每次读写内存前都手动设置。

Bank1 - NOR/PSRAM 1一共有64MB的寻址空间（26位地址线），我们只用了其中1MB的地址空间（19位地址线+1位）。那么有没有办法把这64MB都用完呢？答案是肯定的。我们可以用一个6-64线译码器来译码，接上64个这样的SRAM芯片，总容量为64MB，占用的地址空间刚好就是64MB。当然实际上肯定没有6-64线的译码器，得用很多更小的译码器（如2-4译码器、3-8译码器和4-16译码器等）来拼接。

我们以2-4译码器（如74HC139）为例，如图所示：

输入端接单片机上的地址线A19~20，每个输出端通过一个或门接到每个SRAM芯片的NE3片选引脚上，或门的另一个输入端接单片机上的NE1引脚，即PD7。低地址段A18~0全部接到一起。

当PD7=0（有效），且A20~19=01时，译码器的输出端DCBA为1101，NE3(2)=0，此时刚好选中了第二片SRAM。

当PD7=1（无效）时，或门的输出端全为1，4片SRAM都没有被选中。

用5片2-4译码器可以构成3-8译码器，可以接8个SRAM芯片，用掉4MB的地址空间，容量为8MB。这样接下去，理论上肯定是能把64MB的地址空间都用完的。

如果用上译码器上本身的使能信号E，把它接到PD7上，那么我们就不需要接4个或门了。直接把输出端接到每个SRAM的NE3上就行了。

74HC154就是一个4-16译码器，输出端低电平有效，可以挂接16个SRAM芯片。

假设我们真的用完了这64MB的地址空间，且每个SRAM芯片都是16位的，那么使用的地址线则是A24~0，不是A25~0。A25这根地址线只能用于8位的存储器芯片。

STM32中的地址只能访问一个字节，若我们访问的地址是addr = 0x63E24567，那么实际在地址线A24~0上输出的地址是(addr & 0x3FFFFFF) >> 1 = 0x1F122B3 = 0b1111100010010001010110011，addr的最后一位反映在NBL1~0上。